Polyester process using a pipe reactor

ABSTRACT

The invention is directed to polyester processes that utilizes a pipe reactor in the esterification, polycondensation, or both esterification and polycondensation processes. Pipe reactor processes of the present invention have a multitude of advantages over prior art processes including improved heat transfer, volume control, agitation and disengagement functions.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of copending U.S.Application Ser. No. 10/013,318, filed Dec. 7, 2001, which claimspriority to U.S. Provisional Application Serial No. 60/254,040, filedDec. 7, 2000; both priorapplications are hereby incorporated byreference in their entirety to the extent that they do not contradictstatements herein.

BACKGROUND OF THE INVENTION Field of the Invention

[0002] This invention relates generally to polyester processes andapparatuses, wherein the esterification, polycondensation, or bothesterification and polycondensation process is performed in a pipereactor.

[0003] As the business of manufacturing polyesters becomes morecompetitive, alternative manufacturing processes have become highlydesirable. A variety of processes have been developed. Early effortsused reactive distillation (U.S. Pat. No. 2,905,707) with ethyleneglycol (“EG”) vapor as reactants (U.S. Pat. No. 2,829,153). Multiplestirred pots have been disclosed to gain additional control of thereaction (U.S. Pat. No. 4,110,316 and WO 98/10007). U.S. Pat. No.3,054,776 discloses the use of lower pressure drops between reactors,while U.S. Pat. No. 3,385,881 discloses multiple reactor stages withinone reactor shell. These designs were improved to solve problems withentrainment or plugging, heat integration, heat transfer, reaction time,the number of reactors, etc., as described in U.S. Pat. Nos. 3,118,843;3,582,244; 3,600,137; 3,644,096; 3,689,461; 3,819,585; 4,235,844;4,230,818; and 4,289,895. Unfortunately, these reactors and plants areextremely complex. For example, the stirred polycondensation reactorshave complex designs, which require detailed calculations andcraftsmanship. The reactor must operate under a vacuum and, whetherheated or cooled, maintain its shape so the agitator does not scrape thewalls, and a close tolerance is maintained to provide effective masstransfer. Such complex designs cannot be built or installed quickly andrequire expertise to maintain and operate.

[0004] Conventional cylindrical esterification or ester exchangereactors, such as a continuous stirred tank reactor (“CSTR”) have manyinternals, such as baffles, pipe coils for heating, large overflowweirs, trays, packing, agitators, and draft tubes, etc. Esterificationor ester exchange reactors can also be reactive distillation, stripper,or rectification columns with their associated internal trays, packing,downcomers, reboilers, condensers, internal heat exchangers, refluxsystems, pumps, etc. Conventional polycondensation reactors, which aretypically a psuedo, plug flow device, which tries to maintain an averageresidence time with a narrow time distribution, are typically a (1)CSTR, typically of the wipe film or thin film reactor type, or (2)reactive distillation device. Such conventional condensation reactorscommonly have a means of enhancing the surface renewal, usually bymaking thin films of the polymer. Such conventional polycondensationdevices contain trays, internal heating coils, weirs, baffles, wipefilms, internal agitators, and large agitators with seals or magneticdrives, etc. These reactors normally have scrapers or other highlycomplicated devices for keeping the vapor lines from plugging. Manypolycondensation reactors also have very tight tolerance requirementsand must maintain their shape over a range of temperatures. Thesecylindrical reactors require a large amount of engineering, drafting,and skilled craftsmanship to construct. The cylindrical reactor also hasa specially fabricated jacket having multiple partial pipe jackets andweld lines connecting the pipe jackets to each other and the reactor.The cylindrical reactor has additional external components such asgearboxes, agitators, seal systems, motors, and the like. The extracomplexity, materials, and skill required to construct the cylindricalreactors leads to the higher cost.

[0005] A pipe has been disclosed in prior art patents that is integratedinto the process or equipment. U.S. Pat. No. 3,192,184, for example,discloses an internally baffled pipe within the reactor, and U.S. Pat.No. 3,644,483 discloses the use of a pipe for paste addition. As otherexamples, Patent Application WO 96/22318 and U.S. Pat. No. 5,811,496disclose two pipe reactors between the esterification and polymerizationreactors, and U.S. Pat. No. 5,786,443 discloses a pipe reactor betweenan esterification reactor and a heater leading to a staged reactor. Eachof these reactor trains incorporates a pipe reactor into the othercomplex reactors and equipment.

[0006] While it has been theorized that optimum ester exchange oresterification would occur in a continuum of continuous pressurereduction and continuous temperature increase (see FIG. 1, Santosh K.Gupta and Anil Kumar, Reaction Engineering of Step GrowthPolymerization, The Plenum Chemical Engineering Series, Chapter 8,Plenum Press, 1987), the cost of doing so with existing conventionalequipment is prohibitive, because it requires numerous small reactors,each with their own associated instruments and valves for level,pressure, and temperature control and pumps. Thus, in conventionalpolyester plant designs the number of pressure reduction stages(cylindrical reactors) is minimized to minimize cost. The tradeoff isthat if the number of reactors were instead increased, then the pressuredrop would be minimized.

[0007] There is a need in the art for simpler apparatuses and processesfor making polyesters.

SUMMARY OF THE INVENTION

[0008] The present invention relates to equipment and processes for themanufacture of polyesters. More specifically, the present inventionrelates to pipe reactors and associated equipment and processes for usein both new and existing (retrofitted) polyester plants. The startingmaterials, or the reactants, can be liquid, gas, or solid feedstocksusing any components for the polyester or modifiers. The present pipereactor invention has many advantages over conventional polyesterprocesses and apparatuses.

[0009] This pipe reactor process of the present invention allows thedesigner to decouple from each other the reactor heat transfer, volume(i.e. residence time), agitation, and disengagement functions. Withrespect to heat transfer, the pipe reactors of the present invention donot require internal heating coils of a continuous stirred tank reactor,but instead can use various heating means such as a heat exchanger orjacketed pipe. Among many limitations of CSTRs, the amount of heatingcoils is limited due to the need to maintain agitation of the fluids.Too many heating coils do not allow enough space between coils foragitation. Because the heat transfer function and agitation function aredecoupled in a pipe reactor system, this limitation of CSTRs, amongothers, is not present in the pipe reactor system of the presentinvention.

[0010] Pipe reactors are not limited to the volume of a vessel forkinetic considerations as is the case with a CSTR; pipe reactors utilizethe length of pipe for kinetics, which can be varied in a simple manner.As to mass transfer or agitation, pipe reactors do not require apropeller or impeller of a CSTR; instead, a pump or gravity flow can beused to move fluid around.

[0011] With respect to disengagement, which is the separation of the gasfrom the liquid interface, a CSTR process controls the liquid/gasinterface by reactor volume. Controlling the interface by controllingthe reactive volume is a difficult way to control the velocity of thefluids. If the CSTR is made tall and skinny, the level control becomesdifficult, agitator shaft deflections and seal problems increase, vaporvelocities increase with increased entrainment, and reactor costsincrease with the increased surface area. On the other hand, if the CSTRis made short and fat, not enough heating coils can be introduced intothe reactor, agitation is more difficult with the larger diameter, andfor large scale plants, shipping the vessel becomes an issue. Thus,there are optimum dimensions for the length, width and height of a CSTR,which thereby makes it difficult to modify the CSTR to control to thevelocity of the fluids. As such, in a CSTR operation, more vapor removaloperations are required to control the vapor velocity. However,additional vapor removal operations lead to the problems of entrainedliquid being removed by the vapor and loss of yield. Conversely, in apipe reactor system of the invention herein, to control the liquid/gasinterface, additional pipes (pipe reactors) in parallel can be added tocontrol the total fluid velocity and gas velocity leaving the surface.Thus, with a pipe reactor system of the present invention, thedisengagement functions are simpler and much easier to control than thatof a conventional CSTR system. Similar disadvantages can be found inother conventional reactor systems for making polyesters found in theart, such as reactive distillation, stripper, or rectification columns,or tank with internals, screw, or kneader reactors in comparison to theabove stated advantages of the pipe reactor design of the presentinvention.

[0012] Surprisingly, the pipe reactors of the present invention can beused for polyester processes, which typically have long residence times.Generally, pipe reactors are used for processes having only very shortresidence times. However, it has been found herein that the pipereactors of the present invention can be used for longer residence timepolyester production processes.

[0013] Accordingly, in one embodiment, the invention is directed to aprocess for making a polyester polymer from a plurality of reactants,comprising:

[0014] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface, the esterification pipe reactorcomprising a substantially empty pipe;

[0015] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0016] c. providing a polycondensation pipe reactor formed separately ofthe esterification pipe reactor, the polycondensation pipe reactor influid communication with the esterification pipe reactor, thepolycondensation pipe reactor having a first end, a second end, and aninside surface, the polycondensation pipe reactor comprising asubstantially empty pipe; and

[0017] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0018] In another embodiment, the invention is directed to a process formaking a polyester polymer from a plurality of reactants, comprising:

[0019] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0020] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid, wherein the reactantscomprise terephthalic acid or dimethylterephthalate;

[0021] c. providing a polycondensation pipe reactor formed separately ofthe esterification pipe reactor, the polycondensation pipe reactor influid communication with the esterification pipe reactor, thepolycondensation pipe reactor having a first end, a second end, and aninside surface; and

[0022] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0023] In another embodiment, the invention is directed to a process formaking a polyester polymer from a plurality of reactants, comprising:

[0024] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0025] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0026] c. providing a polycondensation pipe reactor formed separately ofthe esterification pipe reactor, the polycondensation pipe reactor influid communication with the esterification pipe reactor, thepolycondensation pipe reactor having a first end, a second end, and aninside surface; and

[0027] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0028] In another embodiment, the invention is directed to a process formaking a polyester polymer from a plurality of reactants, comprising:

[0029] a. providing a combined esterification and prepolymerpolycondensation pipe reactor having an inlet, an outlet, and aninterior surface;

[0030] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester oligomer within the pipe reactor andthe polyester oligomer exits from the outlet thereof, wherein thereactants and the polyester oligomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0031] c. providing a polycondensation pipe reactor formed separately ofthe combined esterification prepolymer pipe reactor, thepolycondensation pipe reactor in fluid communication with theesterification/prepolymer pipe reactor, the polycondensation pipereactor having a first end, a second end, and an inside surface; and

[0032] d. directing the fluid polyester oligomer into the first end ofthe polycondensation pipe reactor so that the oligomer flows through thepolycondensation reactor, the oligomer reacting to form the polymerwithin the polycondensation pipe reactor, and the polymer exits from thesecond end of the reactor, wherein the oligomer and the polymer flowingthrough the polycondensation pipe reactor are each a polycondensationfluid.

[0033] In another embodiment, the invention is directed to a process formaking a polyester polymer from a plurality of reactants, comprising:

[0034] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0035] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0036] c. providing a polycondensation pipe reactor integrally combinedwith the esterification pipe reactor, the polycondensation pipe reactorin fluid communication with the esterification pipe reactor, thepolycondensation pipe reactor having a first end, a second end, and aninside surface; and

[0037] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0038] In another embodiment, the invention is directed to a process formaking a polyester oligomer from a plurality of reactants, comprising:

[0039] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0040] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0041] c. providing a prepolymer polycondensation pipe reactor formedseparately of the esterification pipe reactor, the polycondensation pipereactor in fluid communication with the esterification pipe reactor, thepolycondensation pipe reactor having a first end, a second end, and aninside surface; and

[0042] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form the oligomerwithin the polycondensation pipe reactor, and the oligomer exits fromthe second end of the reactor, wherein the monomer and the oligomerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0043] In another embodiment, the invention is directed to a process formaking a polyester oligomer from a plurality of reactants, comprising:

[0044] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0045] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor and reactwith each other to form a polyester monomer within the pipe reactor andthe polyester monomer exits from the outlet thereof, wherein thereactants and the polyester monomer flowing through the esterificationpipe reactor are each an esterification fluid;

[0046] c. providing a prepolymer polycondensation pipe reactorintegrally combined with the esterification pipe reactor, thepolycondensation pipe reactor in fluid communication with theesterification pipe reactor, the polycondensation pipe reactor having afirst end, a second end, and an inside surface; and

[0047] d. directing the fluid polyester monomer into the first end ofthe polycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form the oligomerwithin the polycondensation pipe reactor, and the oligomer exits fromthe second end of the reactor, wherein the monomer and the oligomerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0048] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0049] a. providing an esterification pipe reactor having an inlet, anoutlet, an interior surface, and at least one weir attached to theinterior surface thereof; and

[0050] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, wherein the reactants and the polyester monomer flowing throughthe esterification pipe reactor are each an esterification fluid, andwherein the esterification fluids flow over the weir.

[0051] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0052] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0053] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, and wherein the reactants and the polyester monomer flowingthrough the esterification pipe reactor are each an esterificationfluid; and

[0054] c. recirculating a portion of the process fluids and directingthe recirculation effluent back to and therethrough the esterificationreactor proximate the inlet of the esterification reactor or between theinlet and outlet of the esterification reactor.

[0055] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0056] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0057] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, wherein the reactants and the polyester monomer flowing throughthe esterification pipe reactor are each an esterification fluid; and

[0058] c. removing vapors from the pipe reactor intermediate its inletand its outlet and/or proximate its outlet through a vent of empty pipe.

[0059] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0060] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface, the inlet being positioned at least 20vertical feet below the outlet;

[0061] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, and wherein the reactants and the polyester monomer flowingthrough the esterification pipe reactor are each an esterificationfluid.

[0062] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0063] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface;

[0064] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, wherein the reactants and the polyester monomer flowing throughthe esterification pipe reactor are each an esterification fluid, andwherein the fluids present in the pipe reactor are in a bubble or frothflow regime.

[0065] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0066] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface, wherein the pipe reactor hasalternating linear and non-linear sections extending in its lengthwisedirection between the inlet and outlet thereof,

[0067] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, wherein the reactants and the polyester monomer flowing throughthe esterification pipe reactor are each an esterification fluid.

[0068] In another embodiment, the invention is directed to a process formaking a polyester monomer from a plurality of reactants, comprising:

[0069] a. providing an esterification pipe reactor having an inlet, anoutlet, and an interior surface; and

[0070] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, thereactants reacting with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof, wherein the at least one reactant and the polyester monomerflowing through the esterification pipe reactor are each anesterification fluid.

[0071] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0072] a. providing a polycondensation pipe reactor having a first end,a second end, and an inside surface, the first end being disposedvertically above the second end, the polycondensation pipe reactorhaving alternating linear and non-linear sections extending in itslengthwise direction between its first end and its second end; and

[0073] b. directing a fluid polyester monomer into the first end of thepolycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid.

[0074] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0075] a. providing a polycondensation pipe reactor having a first end,a second end, an inside surface, and at least one weir attached to theinside surface thereof, wherein the pipe reactor is made of asubstantially empty pipe; and

[0076] b. directing a fluid polyester monomer into the first end of thepolycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid, and wherein at least one of the polycondensationfluids flows over the weir.

[0077] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0078] a. providing a polycondensation pipe reactor having a first end,a second end, and an inside surface; and

[0079] b. directing a fluid polyester monomer into the first end of thepolycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid; and

[0080] c. removing vapors from the pipe reactor intermediate its inletand its outlet and/or proximate its inlet or outlet through a ventcomprising substantially empty pipe.

[0081] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0082] a. providing a polycondensation pipe reactor having a first end,a second end, and an inside surface; and

[0083] b. directing a fluid polyester monomer into the first end of thepolycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacting to form an oligomer andthen the oligomer reacting to form the polymer within thepolycondensation pipe reactor, and the polymer exits from the second endof the reactor, wherein the monomer, the oligomer, and the polymerflowing through the polycondensation pipe reactor are each apolycondensation fluid, and wherein the fluids present in the pipereactor are in a stratified flow regime.

[0084] In another embodiment, the invention is directed to a a processfor making a polyester polymer, comprising:

[0085] a. providing a polycondensation pipe reactor having a first end,a second end, and an inside surface; and

[0086] b. directing a fluid polyester monomer into the first end of thepolycondensation pipe reactor so that the monomer flows through thepolycondensation reactor, the monomer reacts to form an oligomer andthen the oligomer reacts to form the polymer within the polycondensationpipe reactor, and the polymer exits from the second end of the reactor,wherein the monomer, the oligomer, and the polymer flowing through thepolycondensation pipe reactor are each a polycondensation fluid.

[0087] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0088] a. providing a polycondensation pipe reactor having a first end,a second end, and an inside surface; and

[0089] b. directing a fluid polyester oligomer into the first end of thepolycondensation pipe reactor so that the oligomer flows through thepolycondensation pipe reactor, the oligomer reacting to form thepolyester polymer within the polycondensation pipe reactor and thepolyester polymer exits from the second end thereof.

[0090] In another embodiment, the invention is directed to an apparatusfor producing a polyester polymer, comprising:

[0091] a. an esterification pipe reactor having an inlet, an outlet, andan interior surface through which esterification fluid reactants arepassed; and

[0092] b. a polycondensation pipe reactor formed separately of and influid communication with the esterification reactor, wherein thepolycondensation reactor has an inlet, an outlet, and an interiorsurface through which at least one polycondensation fluid reactant ispassed,

[0093] wherein the esterification and polycondensation reactors comprisesubstantially empty pipe.

[0094] In another embodiment, the invention is directed to an apparatusfor producing a polyester polymer, comprising:

[0095] a. an esterification pipe reactor having an inlet, an outlet, andan interior surface through which esterification fluid reactants arepassed; and

[0096] b. a polycondensation pipe reactor formed separately of and influid communication with the esterification reactor, wherein thepolycondensation reactor has an inlet, an outlet, and an interiorsurface through which at least one polycondensation fluid reactant ispassed.

[0097] In another embodiment, the invention is directed to anesterification pipe reactor apparatus for producing a polyester monomer,comprising:

[0098] a. an esterification pipe reactor having an inlet, an outlet, andan interior surface; and

[0099] b. a recirculation loop having an influent and an effluent, theeffluent being in fluid communication with the esterification pipereactor.

[0100] In another embodiment, the invention is directed to an apparatusfor producing a polyester monomer, oligomer, or polymer, comprising:

[0101] a. a pipe reactor having an inlet, an outlet, and an interiorsurface through which the fluid reactants are passed; and

[0102] b. a weir connected to a portion of the interior surface of thepipe reactor and adjacent the outlet thereof,

[0103] wherein the reactor comprises substantially empty pipe.

[0104] In another embodiment, the invention is directed to an apparatusfor producing a polyester monomer, oligomer, or polymer, comprising:

[0105] a. a pipe reactor having an inlet, an outlet, and an interiorsurface through which the fluid reactants are passed; and

[0106] b. a vent in fluid communication with the reactor, the ventfurther comprising an upstanding degas stand pipe coupled to the vent,the degas stand pipe having a receiving end in fluid communication withthe vent and an opposed venting end disposed vertically above thereceiving end, and wherein the degas stand pipe is non-linear extendingin its lengthwise direction between the receiving end and the ventingend thereof, and wherein the degas stand pipe is formed of threecontiguous sections each in fluid communication with each other, a firstsection adjacent the receiving end and extending substantiallyvertically from the vent, a second section coupled to the first sectionand oriented at an angle relative to the first section in plan view, anda third section coupled to the second section and oriented at acomplimentary angle relative to the second section in plan view so thatthe third section is oriented substantially horizontally.

[0107] In another embodiment, the invention is directed to an apparatusfor producing a polyester monomer, oligomer, or polymer comprising:

[0108] a. a pipe reactor having an inlet, an outlet, and an interiorsurface through which the fluid reactants are passed.

[0109] In another embodiment, the invention is directed to an apparatusfor venting a process of gas or vapor while effectively disengagingliquid from the gas or vapor, the liquid, gas, and vapor being fluids,separating the liquid from the gas or vapor, and returning the liquidback to the process, comprising:

[0110] a. a vessel or process pipe containing (i) liquid and (ii) gas orvapor; and

[0111] b. a vent in fluid communication with the vessel or process pipe,the vent further comprising an upstanding degas stand pipe coupled tothe vent, the degas stand pipe having a receiving end in fluidcommunication with the vent and an opposed venting end disposedvertically above the receiving end, and wherein the degas stand pipe isnon-linear extending in its lengthwise direction between the receivingend and the venting end thereof, and wherein the degas stand pipe isformed of three contiguous sections each in fluid communication witheach other, a first section adjacent the receiving end and extendingsubstantially vertically from the vent, a second section coupled to thefirst section and oriented at an angle relative to the first section inplan view, and a third section coupled to the second section andoriented at an angle relative to the second section in plan view so thatthe third section is oriented substantially horizontally.

[0112] In another embodiment, the invention is directed to a fluidmixing and distribution system adapted for the mixture, storage, anddistribution of fluids to a separate plant process distribution system,comprising:

[0113] a. a first elongate and vertically disposed fluid storage vessel;

[0114] b. a circulating pump in fluid communication with the firstvessel and the second vessel, the circulating pump being constructed andarranged to pass a fluid flow through the system and to circulate thefluid from the first vessel into the second vessel and from the firstvessel to the first vessel;

[0115] c. a second fluid storage and dispensing vessel in fluidcommunication with the first vessel and the second vessel being disposedat a greater vertical elevation than the first vessel; and

[0116] d. a control valve in fluid communication with the circulatingpump, the first vessel and the second vessel, respectively, the controlvalve being constructed and arranged to selectively direct the fluidflow from the first vessel into the second vessel and from the firstvessel into the first vessel,

[0117] wherein the second vessel is in fluid communication with theplant process distribution system, and wherein a static pressure headformed by the fluid held within the second vessel is used to pass thefluid from the second vessel to the plant process distribution system.

[0118] In another embodiment, the invention is directed to a fluidmixing and distribution system adapted for the mixture, storage, anddistribution of fluids to a separate plant process distribution system,comprising:

[0119] a. a first fluid storage vessel;

[0120] b. a second fluid mixing and storage vessel;

[0121] c. a circulating pump in fluid communication with the firstvessel and the second vessel, the circulating pump being constructed andarranged to circulate the fluid through the system and from the firstvessel into the second vessel;

[0122] d. the second vessel being disposed at a greater verticalelevation than both of the first vessel and the plant processdistribution system; and

[0123] e. a control valve in fluid communication with the circulatingpump, the first vessel and the second vessel, respectively, the controlvalve being constructed and arranged to selectively direct the fluidflow from the first vessel back into the first vessel and from the firstvessel into the second vessel;

[0124] f. the second vessel being in fluid communication with the plantprocess distribution system, wherein a static pressure head formed bythe fluid held within the second vessel is used to pass the fluid fromthe second vessel to the plant process distribution system.

[0125] In another embodiment, the invention is directed to a method ofmixing and distribution a fluid within a fluid mixing and distributionsystem adapted for the mixture, storage, and distribution of fluids to aseparate plant process distribution system, comprising:

[0126] a. placing at least one fluid into a first elongate andvertically disposed fluid storage vessel;

[0127] b. passing the fluid from the first vessel into a second elongateand vertically disposed fluid mixing and storage vessel, the secondfluid vessel being disposed at a greater vertical elevation than both ofthe first vessel and the plant process distribution system, with acirculating pump in fluid communication with the first vessel and thesecond vessel, the circulating pump being constructed and arranged topass the fluid through the system;

[0128] c. using a control valve in fluid communication with thecirculating pump, the first vessel and the second vessel to selectivelydirect the fluid from the first vessel to either of the first vessel andthe second vessel; and

[0129] d. selectively passing the fluid from the second vessel to theplant process distribution system, the second vessel creating a staticpressure head used to pass the fluid stored therein to the plant processdistribution system.

[0130] In another embodiment, the invention is directed to a heattransfer media control system for use with a pipe reactor system, thepipe reactor system having a supply heat transfer media loop throughwhich a first stream of a heat transfer media is passed and a returnheat transfer media loop through which a second stream of the heattransfer media is passed, the temperature of the first heat transfermedia stream being greater than the temperature of the second heattransfer media stream, said heat transfer media control systemcomprising:

[0131] a. a first heat transfer media header through which the firstheat transfer media stream is passed;

[0132] b. a second heat transfer media header through which the secondheat transfer media stream is passed;

[0133] c. a first heat transfer media sub-loop, through which the heattransfer media may be passed, from the first to the second headers,respectively;

[0134] d. a control valve in fluid communication with a selected one ofthe headers and the first sub-loop;

[0135] e. the pressure of the first heat transfer media stream withinthe first header being greater than the pressure of the second heattransfer media stream within the second header;

[0136] f. wherein the control valve is used to selectively direct atleast a portion of the first heat transfer media stream into the firstsub-loop using the pressure of the first heat transfer media stream topass the heat transfer media, and to also control the temperature andpressure of the heat transfer media stream being passed through thefirst sub-loop.

[0137] In another embodiment, the invention is directed to a heattransfer media control system for use with a pipe reactor system, thepipe reactor system having a supply heat transfer media loop throughwhich a first stream of a heat transfer media is passed and a returnheat transfer media loop through which a second stream of the heattransfer media is passed, the temperature of the first heat transfermedia stream being greater than the temperature of the second heattransfer media stream, said heat transfer media control systemcomprising:

[0138] a. a first heat transfer media header through which the firstheat transfer media stream is passed;

[0139] b. a second heat transfer media header through which the secondheat transfer media stream is passed;

[0140] c. a first heat transfer media sub-loop through which the heattransfer media may be passed from the first header to the second header;

[0141] d. a first control valve in fluid communication with the firstheader and the first sub-loop; and

[0142] e. a second control valve in fluid communication with the firstsub-loop and the second header;

[0143] f. the pressure of the first heat transfer media stream withinthe first header being greater than the pressure of the second heattransfer media stream within the second header;

[0144] g. wherein one or both of the control valves is used toselectively direct at least a portion of the first heat transfer mediastream into the first sub-loop, using the pressure of the first heattransfer media stream, to pass the heat transfer media through the firstsub-loop, and to also control the temperature and pressure of the heattransfer media stream being passed through the first sub-loop.

[0145] In another embodiment, the invention is directed to a method ofpassing a heat transfer media through a heat transfer media system foruse with a pipe reactor system, the pipe reactor system having a supplyheat transfer media loop through which a first stream of a heat transfermedia is passed and a return heat transfer media loop through which asecond stream of the heat transfer media is passed, the temperature andthe pressure of the first heat transfer media stream being greater thanthe temperature and the pressure of the second heat transfer mediastream, said heat transfer media control system comprising:

[0146] a. passing the first heat transfer media stream through a firstheat transfer media header;

[0147] b. passing the second heat transfer media stream through a secondheat transfer media header;

[0148] c. passing the heat transfer media from the first header througha first heat transfer media sub-loop, in the absence of a heat transfermedia circulating pump, with a first control valve in fluidcommunication with the first header and the first sub-loop; and

[0149] d. passing the heat transfer media from the first sub-loop intothe second header, in the absence of a heat transfer media circulatingpump, with a second control valve in fluid communication with the firstsub-loop and the second header.

[0150] In another embodiment, the invention is directed to a fluiddelivery system for the delivery of a process working fluid supply to afluid process plant, the process plant having a pipe system forhandling, distributing, and processing the fluid, the system comprising:

[0151] a. at least one delivery container positioned at a pump station;and

[0152] b. at least one pump in fluid communication with the at least onedelivery container;

[0153] c. said at least one delivery container being in fluidcommunication with a valve train, the valve train being in fluidcommunication with the process plant pipe system;

[0154] wherein the fluid is selectively pumped directly from the atleast one delivery container through the valve train and into theprocess plant pipe system in the absence of a fluid delivery feed andstorage tank for otherwise receiving and storing the fluid from the atleast one delivery container therein.

[0155] In another embodiment, the invention is directed to a fluiddelivery system for the delivery of a process working fluid supply to afluid process plant, the process plant having a pipe system forhandling, distributing, and processing the fluid, the system comprising:

[0156] a. a first delivery container positioned at a pump station;

[0157] b. a first pump in fluid communication with the first deliverycontainer;

[0158] c. a second delivery container positioned at the pump station;and

[0159] d. a second pump in fluid communication with the second deliverycontainer;

[0160] e. each of the delivery containers and pumps, respectively, beingin fluid communication with a valve train, the valve train beingcomprised of a plurality of selectively operable control valves andbeing in fluid communication with the process plant pipe system;

[0161] wherein the fluid is selectively pumped directly from the firstand second delivery containers, respectively, through the valve trainand into the process plant pipe system in the absence of a fluiddelivery feed and storage tank.

[0162] In another embodiment, the invention is directed to a fluiddelivery method for use in delivering a supply of a process workingfluid to a fluid process plant, the process plant having a pipe systemfor handling, distributing, and processing the fluid, the systemcomprising:

[0163] a. positioning a first delivery container at a pump station, thefirst delivery container being in fluid communication with a first pump;

[0164] b. positioning a second delivery container at the pump station,the second delivery container being in fluid communication with a secondpump;

[0165] c. selectively pumping the fluid from each of the respectivedelivery containers directly into a valve train, the valve train beingcomprised of a plurality of selectively operable control valves in fluidcommunication with the process plant pipe system, and through the valvetrain into the process plant pipe system in the absence of a fluiddelivery feed and storage tank for otherwise receiving and storing thefluid from the at least one delivery container therein.

[0166] In another embodiment, the invention is directed to an integratedplant water distribution system, the water distribution system beingseparately supplied with clean, fresh water from a water supply sourcefor use within a process plant, the system comprising:

[0167] a. a safety shower water storage tank in fluid communicationwith, and supplied by water from the water source;

[0168] b. a first water distribution loop in fluid communication withthe safety shower water storage tank and being supplied with watertherefrom;

[0169] c. a second water distribution loop in fluid communication withthe first water distribution loop; and

[0170] d. means for selectively drawing water from the first waterdistribution loop to supply water to the second water distribution loop.

[0171] In another embodiment, the invention is directed to a method ofdistributing water through an integrated plant water distributionsystem, the water distribution system being separately supplied withclean, fresh water from a water source for use within a process plant,the method comprising:

[0172] a. supplying water to a safety shower water storage tank;

[0173] b. passing the water from the safety shower water storage tankinto a first water distribution loop in fluid communication with thewater storage tank;

[0174] c. selectively passing water from the first water distributionloop to a second water distribution loop in fluid communication with thefirst water loop.

[0175] In another embodiment, the invention is directed to an integratedvacuum system for use with a final polycondensation reactor havingseparate high pressure, medium pressure, and low pressurepolycondensation vacuum zones, respectively, the system comprising:

[0176] a. a spray condenser, said spray condenser being in fluidcommunication with each of the medium and low pressure vacuum zones,respectively, of the polycondensation reactor;

[0177] b. an interstage condenser in fluid communication with the spraycondenser; and

[0178] c. a vacuum pump in fluid communication with the interstagecondenser.

[0179] In another embodiment, the invention is directed to an integratedvacuum system for use with a final polycondensation reactor having atleast a medium pressure polycondensation vacuum zone and a separate lowpressure polycondensation vacuum zone, the system comprising:

[0180] a. a spray condenser, said spray condenser being in fluidcommunication with each of the medium and low pressure vacuum zones,respectively, of the polycondensation reactor;

[0181] b. a first EG jet in fluid communication with the spraycondenser;

[0182] c. an interstage condenser in fluid communication with the firstEG jet;

[0183] d. a vacuum pump in fluid communication with the interstagecondenser; and

[0184] e. a second EG jet in fluid communication with the low pressurevacuum zone and the spray condenser, respectively.

[0185] In another embodiment, the invention is directed to a method ofcollecting fluid from a final polycondensation reactor having a highpressure vacuum zone, a medium pressure vacuum zone, and a low pressurepolycondensation vacuum zone, the method comprising:

[0186] a. passing the fluid from at least the medium pressurepolycondensation vacuum zone and the low pressure polycondensationvacuum zone of the reactor into a single spray condenser in sealed fluidcommunication with each of the medium and low pressure vacuum zones,respectively; and

[0187] b. drawing the fluid through an interstage condenser in fluidcommunication with the spray condenser with a vacuum pump in fluidcommunication with the interstage condenser.

[0188] In another embodiment, the invention is directed to a process formaking a polyester monomer, comprising:

[0189] a. providing a pipe reactor having an inlet, an outlet, and aninterior surface, the inlet disposed elevationally below the outlet; and

[0190] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, whereinthe reactants react with each other to form the polyester monomer withinthe pipe reactor and the polyester monomer exits from the outletthereof.

[0191] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0192] a. providing a polycondensation reactor having a first end, asecond end, and an inside surface, the first end disposed elevationallyabove the second end, the polycondensation reactor being non-linearbetween the first end and the second end; and

[0193] b. directing a fluid polyester monomer into the first end of thepolycondensation reactor so that the monomer flows through thepolycondensation reactor, wherein the monomer reacts to form the polymerwithin the polycondensation reactor and the polymer exits from thesecond end thereof.

[0194] In another embodiment, the invention is directed to a process formaking a polyester polymer, comprising:

[0195] a. providing a polycondensation reactor having a first end, asecond end, and an inside surface, the first end disposed elevationallyabove the second end, wherein the polycondensation reactor forms anangle with a vertically-oriented plane, the angle being greater thanzero degrees; and

[0196] b. directing a fluid monomer into the first end of thepolycondensation reactor so that the monomer flows through ofpolycondensation reactor, wherein the monomer reacts to form thepolyester polymer within the polycondensation reactor and the polyesterpolymer exits from the second end thereof.

[0197] In another embodiment, the invention is directed to a process formaking a polyester, comprising:

[0198] a. providing a pipe reactor having an inlet, an outlet, and aninterior surface, the inlet disposed elevationally below the outlet; and

[0199] b. adding at least one reactant into the pipe reactor proximalthe inlet so that the reactants flow through the pipe reactor, whereinthe reactants react with each other to form the polyester within thepipe reactor and the polyester exits from the outlet thereof.

[0200] In another embodiment, the invention is directed to an apparatusfor reacting reactants into a polyester monomer, comprising:

[0201] a. a pipe reactor having an inlet, an outlet, and an interiorsurface, the inlet disposed elevationally below the outlet; and

[0202] b. a weir connected to a portion of the interior surface of thepipe reactor adjacent the outlet thereof.

[0203] In another embodiment, the invention is directed to an apparatusfor reacting reactants into a polyester monomer, comprising:

[0204] a. a pipe reactor having an inlet, an outlet, and an interiorsurface, the inlet disposed elevationally below the outlet; and

[0205] b. a venting mechanism incorporated into the pipe reactor so thata fluid traversing within its interior surface also flows through theventing mechanism when flowing from the inlet to the outlet of the pipereactor, the venting mechanism comprising an eccentric flat-on-bottomreducer.

[0206] In another embodiment, the invention is directed to an apparatusfor reacting reactants into a polyester monomer, comprising:

[0207] a. a pipe reactor having an inlet, an outlet, and an interiorsurface, the inlet disposed elevationally below the outlet; and

[0208] b. a recirculation loop having an influent and an effluent, theinfluent in fluid communication with the pipe reactor proximal to itsoutlet and the effluent in fluid communication with the pipe reactoradjacent its inlet

[0209] In another embodiment, the invention is directed to an apparatusfor reacting a monomer into a polyester polymer, comprising:

[0210] a. a polycondensation reactor having a first end, a second end,and an inside surface, the first end disposed elevationally above thesecond end, the polycondensation reactor being formed as a plurality ofcontiguous interconnected sections in which the monomer flows along theinside surface of each section traversing from the first end to thesecond end of the polycondensation reactor, wherein adjacent sectionsform non-linear angles with each other; and

[0211] b. at least one weir attached to the inside surface of thepolycondensation reactor, wherein one weir is located adjacent ajuncture of each of the interconnected sections

[0212] In another embodiment, the invention is directed to a process formaking an ester from a plurality of reactants comprising:

[0213] (a) providing an esterification pipe reactor having a first inletand a first outlet;

[0214] (b) adding the reactants under esterification reaction conditionsinto the esterification pipe reactor proximate to the first inlet andforming a two phase flow so the reactants form a liquid phase and vaporphase through the esterification pipe reactor and wherein at least aportion of the reactants form an ester monomer.

[0215] In another embodiement, the invention is directed to a processfor making a polyester from a plurality of reactants comprising:

[0216] (a) providing an esterification pipe reactor having a first inletand a first outlet;

[0217] (b) adding the reactants under esterification reaction conditionsinto the esterification pipe reactor proximate to the first inlet andforming a two phase flow so the reactants form a liquid phase and vaporphase flow through the esterification pipe reactor and wherein at leasta portion of the reactants form an ester monomer;

[0218] (c) reacting the monomer under polycondensation reactionconditions in a polycondensation pipe reactor wherein at least a portionof the ester monomer forms an oligomer; and

[0219] (d) reacting the oligomer under polycondensation reactionconditions in the polycondensation pipe reactor wherein at least aportion of the oligomer forms a polyester.

[0220] In another embodiment, the invention is directed to an apparatusfor preparing of at least one of an ester monomer, an ester oligomer ora polyester comprising a pipe reactor having an inlet, an outlet and aninterior through which reactants of at least one of an ester monomer, anester oligomer or a polyester are passed.

[0221] The present invention provides for apparatuses for each and everyprocess embodiment, and concomitantly a process related to each andevery apparatus of the invention.

[0222] Additional advantages of the invention will be set forth in partin the description which follows, and in part will be obvious from thedescription, or may be easily learned by practice of the invention. Theadvantages of the invention will be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0223] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate severalembodiment(s) of the invention and together with the description, serveto explain the principles of the invention.

[0224]FIG. 1 shows a typical polyester reaction temperature and pressureprofile.

[0225]FIG. 2 shows one embodiment of the esterification or thepolycondensation pipe reactor. In a polycondensation pipe reactor mode,the influent and effluent are reversed (influent at 11 and effluent at12).

[0226]FIG. 3 shows installed costs vs. nominal pipe diameter (inches)for a typical pipe reactor installed cost of this invention.

[0227]FIG. 4 shows one embodiment of the invention wherein the top ofthe ester exchange or esterification reactor where level control occursvia a weir into the polycondensation reactor.

[0228]FIG. 5 shows one embodiment of the invention where an existingpolyester production facility is modified with one or more pipereactors.

[0229]FIG. 6 shows an embodiment of the invention where a larger plantwhere multiple parallel esterification and polycondensation pipereactors are utilized, as well as the production of multiple productswithin one system.

[0230]FIGS. 7 a-g show various embodiments of the vapor disengagementfor both the esterification and polycondensation process.

[0231]FIG. 8 shows an embodiment of the polycondensation vapordisengagement.

[0232]FIG. 9 shows an embodiment of laminar mixing in a polycondensationzone utilizing a weir and a reduced diameter pipe flow inverter systemdownstream of the weir.

[0233]FIG. 10 shows various embodiments of altering the esterificationor ester exchange reactor pressure profile using different non-linearconfigurations. This figure is presented in side view, showing thevertical displacement between each turn of the esterification or esterexchange reactor lines.

[0234]FIG. 11 is a plot of the pressure profiles corresponding to thoseconfigurations of FIG. 10.

[0235]FIGS. 12a and 12 b show different aspects of the additivelocations within the process.

[0236]FIGS. 13a and 13 b show two different embodiments wherein thepaste tank is eliminated by using a recirculation loop.

[0237]FIG. 14 shows an embodiment wherein the heat transfer mediasubloop pumps are eliminated.

[0238]FIG. 15a shows a typical prior art mix and feed system.

[0239]FIG. 15b shows an embodiment of the invention for the mix and feedsystem that eliminates various tanks and other control devices and unitoperations.

[0240]FIG. 16 shows an embodiment of the invention wherein analternating low and high pressure configuration is used for the esterexchange or polycondensation pipe reactor.

[0241]FIGS. 17 a and b show two embodiments of the invention for apolyester plant design integrating a pipe reactor for the esterificationand a pipe reactor for the polycondensation system.

[0242]FIG. 18 shows one embodiment for the polycondensation pipe reactorprocess. FIG. 8 is an exploded view of element 133 and FIG. 9 is anexploded view of element 142.

[0243]FIG. 19 is an embodiment wherein distillation is replaced withadsorption.

[0244]FIG. 20a shows the different flow regimes of two-phase flow inhorizontal pipes.

[0245]FIG. 20b shows the vapor mass flow vs. ratio of liquid over vapormass flow and the relationship to each flow regime of two-phase flow inhorizontal pipes from FIG. 20a. FIG. 20b also identifies the preferredflow regimes for esterification and polycondensation processes of thepresent invention.

[0246]FIG. 21 shows an embodiment of the invention for unloading truckswithout the use of tanks to minimize capital costs and unit operations,along with eliminating water to waste water treatment.

[0247]FIG. 22 shows an embodiment of the invention for combining safetyshower, cooling tower, cutter water and HTM pump coolers to minimize thewater systems in the facility.

[0248]FIG. 23 shows an integrated vacuum system for reducing EG jets andeliminating a chilled water system as one embodiment of the invention.

[0249]FIG. 24 shows the two-phase regimes for esterification andpolycondensation for one embodiment of a process of the presentinvention wherein a pipe reactor is used to produce PET homopolymer.

KEY TO NUMBER DESIGNATIONS IN THE DRAWINGS

[0250] DESIGNATION MEANING 10 pipe reactor 11 outlet 12, inlet 21, 22,23, 24, 25 view 31 inlet 32 fluid outlet 33 gas/vapor outlet 34 inlet 35exit 36 tee 37 eccentric flat-on-bottom reducer 38 weir 41 mix tank 42feed tank level 43 pump 44 agitator 45 temperature controller 46 heatexchanger 47 steam 48 water 49 feed tank 51 level 50 agitator 51 feedtank 52, 53 pump 54 temperature controller 55 steam 56 water 57, 58 feedsystem 59 feed header 60 3-way valve 71 overflow line 72 unjacketed pipe73 jacketed pipe 74 circulating pump 75 level 76 water 77 temperaturecontroller 78 steam 82 feed tank 91 recirculation loop 92 recirculationpump 93 influent 94 pump outlet 95 eductor 96 feeding conduit 97 solidreactant storage device 98 solid metering device 99 feeder 100 inlet101, 102 pipe reactor 103 product outlet 104 vapor outlet 106 tee 110weir 111 inlet 112 post weir 113 outlet 120 inlet 121 vapor outlet 122product outlet 123 reducer 124 weir 125 next elbow 126 pipe cap 127lower end of the reducer pipe 128 tee 133 disengaging system 134 90degree elbow 135 less than 90 degree elbow 136 straight pipe 137 lessthan 90 degree elbow 138 second leg straight pipe 139 tee 140 elbow 141straight pipe line 142 flow inverter system 143 leg 144 third leg 145,146 less than 90 degree elbow 147 vapor outlet 148 product outlet 160,161, 162 flow conduit 163 injection line 164 single esterificationsection inlet 165, 166 parallel pipe reactor flow conduit 171, 172 zone173 return header 174 supply header 181 adsorber bed 182 adsorber bed183 adsorber bed 184 outlet 185 condenser 186 compressor or blower 187condensed stream 188 heat exchanger 189 inlet 190 181 bed outlet 191 182bed inlet 192 182 bed outlet 193 185 condenser outlet/183 bed inlet 194183 bed outlet 195 183 bed outlet 197 inert makeup stream 198 outlet 199inlet to condenser 211, 212, 213 esterification reactor 214 pipe reactor215 pipe reactor 216, 217 vapor outlet line 221 solids tank 222 solidsmetering device 223 weight feeder 224 recirculation line 225 pump 226heat exchanger 227 pipe reactor 228 additional pipe reactoresterification process 229 vent line 230 recycle line 231, 232 vaporline 233 heat exchanger 234 feed point 235, 236, 237 polycondensationreactors 238 gear pump 239 outlet 240 inlet line 241, 242 seal leg 243,244, 245 vent or vacuum header 246 pressure reducing device 247 seal leg251, 252, 253, valve 254, 255, 256, 257, 258, 259, 260, 261, 262 263pump 264 second pump 265 first trailer 266 second trailer 271, 272, 273,automatic valve 274, 275, 276 290 safety shower water storage tank 291safety shower outlet 292 pelletizer water distribution loop 294 filterwater storage tank 295 suitable pump 296 downstream heat exchanger 298filter 299 downstream chemical additive station 300 cutter/pelletizerstation 302 separate water line 303 downstream pump 304 cooling tower306 level control 307 water collection basin 308 cooling tower watersupply loop 310 pump 311 downstream cold water users 312 water purgeline 314 purge controller valve 315 water level control 316 polymersupply line 317 polymer extrusion die head 318 molten polymer strands320 vacuum pump 321 interstage condenser 322 first EG vapor jet 324spray condenser 325 liquid seal vessel 326 filter 328 cooler 330 secondEG jet 331 discharge line 334 vacuum line 335 condenser 336 second sealvessel 337 pump 339 downstream filter 340 chiller 343 control valve 400esterification start 401 esterification end 402 esterificationdisengagement 403 polycondensation start 404 end first stagepolycondensation 405 start second stage polycondensation 406 end secondstage polycondensation

DETAILED DESCRIPTION OF THE INVENTION

[0251] The present invention may be understood more readily by referenceto the following detailed description of preferred embodiments of theinvention and the Examples included therein and to the Figures and theirprevious and following description.

[0252] Before the present compounds, compositions, articles, devices,and/or methods are disclosed and described, it is to be understood thatthis invention is not limited to specific synthetic methods, specificprocesses, or to particular apparatuses, as such may, of course, vary.It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only and is not intended tobe limiting.

[0253] In this specification and in the claims, which follow, referencewill be made to a number of terms which shall be defined to have thefollowing meanings:

[0254] As used in the specification and the appended claims, thesingular forms “a,” “an” and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to apipe reactor includes one or more pipe reactors.

[0255] Ranges may be expressed herein as from “about” one particularvalue, and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

[0256] “Optional” or “optionally” means that the subsequently describedevent or circumstance may or may not occur, and that the descriptionincludes instances where said event or circumstance occurs and instanceswhere it does not. For example, the phrase “optionally heated” meansthat the material may or may not be heated and that such phrase includesboth heated and unheated processes.

[0257] Residue refers to the moiety that is the resulting product of thechemical species in a particular reaction scheme or subsequentformulation or chemical product, regardless of whether the moiety isactually obtained from the chemical species. Thus, an ethylene glycolresidue in a polyester refers to one or more —OCH₂CH₂O— repeat units inthe polyester, regardless of whether ethylene glycol is used to preparethe polyester. Similarly, a sebacic acid residue in a polyester refersto one or more —CO(CH2)₈CO— moieties in the polyester, regardless ofwhether the residue is obtained by reacting sebacic acid or an esterthereof to obtain the polyester.

[0258] As used herein, a prepolymer reactor is the firstpolycondensation reactor, typically under vacuum, and grows the polymerchain length from a feed length of 1-5 to an outlet length of 4-30. Theprepolymer reactor typically has the same function for all polyesters,but some polyesters have a target chain length that is short, such asfrom 10 to 30. For these short target chain length products, no finisherreactor (as defined below) is required, since the prepolymer reactorwill provide the end product. A finisher reactor is the last melt phasepolycondensation reactor, typically under vacuum, and grows the polymerchain to the desired product chain length.

[0259] As used herein, “conventional” process or apparatus with respectto polyester processing refers to a non-pipe reactor or process,including, but not limited to, a continuous stirred tank reactor (CSTR)process or apparatus, or a reactive distillation, stripper, orrectification column process or apparatus, or tank with internals,screw, or kneader process or apparatus. A typical CSTR reactor used in aconventional polycondensation process is a wipe or thin film reactor.

[0260] Reference will now be made in detail to the present preferredembodiment(s) of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused throughout the drawings to refer to the same or like parts.

[0261] The present invention encompasses apparatuses and methods forconverting reactants into a polyester. More specifically, in oneembodiment, in a first step, the present invention reacts startingmaterials (also referred to as raw materials or reactants) into monomers(also referred to as polyester monomers) and then, in a second step, thepresent invention reacts the monomers into oligomers (also referred toas polyester oligomers or prepolymers) and then into the final polyester(also referred to as polymer or polyester polymer). If materials withacid end groups are fed to the first step, such as terephthalic acid orisothalic acid, then the first step is referred to as an esterificationreaction or reactor. If the starting materials have methyl end groups,such as dimethyl terephthalate or dimethyl isothalate, then the firststep or first reactor is an ester exchange step or reactor. Forsimplicity, throughout the specification and claims, esterification andester exchange are used interchangeably and are typically referred to asesterification, but it is understood that esterification or esterexchange depends upon the starting materials. It should also beunderstood that the output from the esterification process can alsocontain oligomer in addition to the monomer. The polycondensationprocess can be one integral process or can be subdivided into twosubparts, a prepolymer process and a finishing process. In theprepolymer process, the output comprises monomer, oligomer, and polymer,with oligomer being typically in the majority. In the finishing process,typically the output from the process comprises oligomer and polymer,with the majority of the output being polymer. In the esterificationprocess, it is possible to have small quantities of polymer exit theprocess. Likewise, in the finishing process, it is possible to havesmall quantities of monomer exiting the process.

[0262] The second step is referred to as the polycondensation process orpolycondensation reactor. In this embodiment, the inlet pressurized sideof the first step or esterification reactor exits at about atmosphericpressure or above, and the output from that first step, which is fedinto the second step, is substantially monomer. In the second step, themonomer is converted to oligomer, which can, if desired, be isolated at,for example, a first pressure separation device such as a seal leg, inthe reactor. If not isolated, the oligomer is further converted to thepolymer in the pipe reactor.

[0263] In an alternative embodiment, the inlet pressurized side of thefirst step exits under vacuum (in one embodiment essentially putting theprepolymer reactor on the top of the ester exchange or esterificationreactor), and oligomer is the substantial product from the first stepand is either isolated as a final product or feeds across to the secondstep in which the oligomer is reacted to form the polymer.

[0264] The invention contemplates many different arrangements for thedifferent reactors. In one embodiment, the esterification reactor is aseparate and distinct reactor from the polycondensation reactor. Monomeris produced in the esterification reactor and is then fed to thepolycondensation reactor to produce polymer. In another embodiment, aprepolymer reactor is put on top of the esterification reactor formingeither a separate or an integral unit, thereby producing oligomer fromthe combined esterification/prepolymer reactor, which is then fed to thepolycondensation reactor. As used herein, integral with reference to thecombination of reactors is intended to mean combining two reactorstogether such that they are in direct fluid communication with eachother and the reactors are essentially indistinguishable from each otherand from one overall reactor system. In another embodiment, thepolycondensation reactor forms an integral unit with the esterificationreactor. Reactants are inputted in the esterification reactor and thefinal polyester polymer product is produced by the integral unit. Inanother embodiment, a prepolymer reactor is used in conjuction with anesterification reactor, either as two separate units or as an integralsingular unit. The oligomer product from the prepolymer reactor isisolated as a final product. Additionally, the invention provides anesterification pipe reactor utilized to make monomer. In another aspect,the invention provides a polycondensation pipe reactor apparatus andprocess. When the esterification and prepolymer reactor are formed as anintegral unit, typically there is a vent line between the reactors tovent off the water by-product; thus, the vent line serves as thecrossover point from the esterification to the prepolymer reactor.

[0265] The process is applicable for any polyester. Such polyesterscomprise at least one dicarboxylic acid residue and at least one glycolresidue; in this context residue should be taken in a broad sense, asfor example, a dicarboxylic acid residue may be formed using adicarboxylic acid or via ester exchange using a diester. Morespecifically suitable dicarboxylic acids include aromatic dicarboxylicacids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylicacids preferably having 4 to 12 carbon atoms, or cycloaliphaticdicarboxylic acids preferably having 8 to 12 carbon atoms. Examples ofdicarboxylic acids comprise terephthalic acid, phthalic acid,isophthalic acid, naphthalene-2,6-dicarboxylic acid,cyclohexanedicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, dipheny-3,4′-dicarboxylic acid,2,2,-dimethyl-1,3-propandiol, dicarboxylic acid, succinic acid, glutaricacid, adipic acid, azelaic acid, sebacic acid, mixtures thereof, and thelike. The acid component can be fulfilled by the ester thereof, such aswith dimethyl terephthalate.

[0266] Suitable diols comprise cycloaliphatic diols preferably having 6to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbonatoms. Examples of such diols comprise ethylene glycol (EG), diethyleneglycol, triethylene glycol, 1,4-cyclohexane-dimethanol,propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol,neopentylglycol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4),2,2,4-trimethylpentane-diol-(1,3), 2-ethylhexanediol-(1,3),2,2-diethylpropane-diol-(1,3), hexanediol-(1,3),1,4-di-(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane,2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2,4,4tetramethylcyclobutanediol, 2,2-bis-(3-hydroxyethoxyphenyl)-propane,2,2-bis-(4-hydroxypropoxyphenyl)-propane, isosorbide, hydroquinone,BDS-(2,2-(sulfonylbis)4,1-phenyleneoxy))bis(ethanol), mixtures thereof,and the like. Polyesters may be prepared from one or more of the abovetype diols.

[0267] Preferred comonomers comprise terephthalic acid, dimethylterephthalate, isophthalic acid, dimethyl isophthalate,dimethyl-2,6-naphthalenedicarboxylate, 2,6-naphthalenedicarboxylic acid,ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol (CHDM),1,4-butanediol, polytetramethyleneglyocl, trans-DMCD, trimelliticanhydride, dimethyl cyclohexane-1,4 dicarboxylate, dimethyl decalin-2,6dicarboxylate, decalin dimethanol, decahydronaphthalane2,6-dicarboxylate, 2,6-dihydroxymethyl-decahydronaphthalene,hydroquinone, hydroxybenzoic acid, mixtures thereof, and the like.Bifunctional (A-B type where the ends are not the same) comonomers, suchas hydroxybenzoic acid may also be included.

[0268] A co-monomer, as in a conventional process, can be added anywherealong the process from the beginning of the esterification to thepolycondensation process. Specifically, with reference to the instantinvention, a co-monomer can be added at a location including, but notlimited to, proximate the inlet to the esterification reactor, proximatethe outlet of the esterification reactor, a point between the inlet andthe outlet of the esterification reactor, anywhere along therecirculation loop, proximate the inlet to the prepolymer reactor,proximate the outlet to the prepolymer reactor, a point between theinlet and the outlet of the prepolymer reactor, proximate the inlet tothe polycondensation reactor, and at a point between the inlet and theoutlet of the polycondensation reactor.

[0269] It should also be understood that as used herein, the termpolyester is intended to include polyester derivatives, including, butnot limited to, polyetheresters, polyester amides and polyetheresteramides. Therefore, for simplicity, throughout the specification andclaims, the terms polyester, polyether ester, polyester amide andpolyetheresteramide may be used interchangeably and are typicallyreferred to as polyester, but it is understood that the particularpolyester species is dependant on the starting materials, i.e.,polyester precursor reactants and/or components.

[0270] The polyesters formed by the process of the present invention arepolyester homopolymers and copolymers that are suitable for use in awide variety of applications including packaging, film, fiber, sheet,coatings, adhesives, molded articles, and the like. Food packaging is aparticularly preferred use for certain polyesters of the presentinvention. In one embodiment, the polyesters comprise a dicarboxylicacid component comprising terephthalic acid or isophthalic acid,preferably at least about 50 mole % terephthalic acid, and in someembodiments, preferably at least about 75 mole % terephthalic acid and adiol component comprising at least one diol selected from ethyleneglycol, cyclohexanedimethanol, diethylene glycol, butanediol andmixtures thereof. The polyesters may further comprise comonomer residuesin amounts up to about 50 mole percent of one or more differentdicarboxylic acids and or up to about 50 mole percent of one or morediols on a 100 mole % dicarboxylic acid and a 100 mole % diol basis. Incertain embodiments comonomer modification of the dicarboxylic acidcomponent, the glycol component or each individually of up to about 25mole % or up to about 15 mole % may be preferred. In one embodiment,dicarboxylic acid comonomers comprise aromatic dicarboxylic acids,esters of dicarboxylic acids, anhydrides of dicarboxylic esters, andmixtures thereof.

[0271] In one embodiment, the reactants comprise terephthalic acid andethylene glycol. In another embodiment, the reactants comprise dimethylterephthalate and ethylene glycol. In yet another embodiment, thereactants comprise terephthalic acid, ethylene glycol, and CHDM.

[0272] Preferred polyesters include, but are not limited to homopolymersand copolymers of polyethylene terephthalate (PET), PETG (PET modifiedwith CHDM comonomer), PBT, fully aromatic or liquid crystallinepolyesters, biodegradable polyesters, such as those comprisingbutanediol, terephthalic acid and adipic acid residues,poly(cyclohexane-dimethylene terephthalate) homopolymer and copolymers,homopolymer and copolymers of CHDM and cyclohexane dicarboxylic acid ordimethyl cyclohexanedicarboxylate, and mixtures thereof. In oneembodiment the polyester is PET made by reacting PTA and EG. In anotherembodiment, the polyester is PETG made by reacting PTA, EG, and CHDM. Inone embodiment, the reactants do not comprise an anhydride. In oneembodiment, the polyester is not polycarbonate or PBT (“polybutyleneterephthalate”), or polyesters made from phthalic anhydride or maleicanhydride.

[0273] The present pipe reactor process may also be used inesterification, polycondensation, or both, for a process whereinterephthalic acid is esterified, hydrogenated, and polymerized to formPET (or PETG if CHDM is also added), such as disclosed in U.S.Application 60/228,695, filed Aug. 29, 2000, and U.S. application Ser.No. 09/812,581, filed Mar. 20, 2001, which are both incorporated hereinby reference.

[0274] The polyesters of the present invention may also contain smallamounts of a trifunctional or tetrafunctional comonomer such astrimellitic anhydride, trimethylolpropane, pyromellitic dianhydride,pentaerythritol, or other polyester forming polyacids or polyolsgenerally known in the art. Crosslinking or branching agents may also beused. In addition, although not required, an additive(s) normally usedin polyesters may be used if desired. Such an additive includes, but isnot limited to one or more of a catalyst, colorant, toner, pigment,carbon black, glass fiber, filler, impact modifier, antioxidant,stabilizer, flame retardant, reheat aid, acetaldehyde reducing compound,oxygen scavenging compound, UV absorbing compound, barrier improvingadditive, such as platelet particles, black iron oxide, and the like.

[0275] When terephthalic acid is used as one of the reactants, typicallypurified terephthalic acid (PTA) is used as the reactant rather thanunpurified terephthalic acid (TPA) or crude TPA (CTA), although TPAand/or CTA can be used in this invention.

[0276] The processes of the present invention are directed to meltpolymerization, that is, the process of the present invention is in themelt phase, wherein the reactants are in a fluid state. This should becontrasted with solid polycondensation as used in certain polyesterprocesses of the prior art; however, the present invention includesprocesses where solid polycondensation follows liquid phasepolycondensation. The pipe reactor process of the present invention isthus appropriate for a fluid process. The polyester polycondensationprocess of the present invention should also be distinguished from otherpolymer processes, such as, for example, emulsion basedpolymerization,which typically requires a second or even further solvent, whereaspolyester condensation does not, and from olefin polymerization, whichis not necessarily a two-step reaction as is the case inpolycondensation.

[0277] The processes of the present invention can achieve completion orsubstantial completion of the esterification reaction at the outlet ofthe esterification or polycondensation process. More specifically, theprocess of the present reaction, in various aspects, can achieve atleast 80% completion, at least 85% completion, at least 90% completion,at least 95% completion, at least 97.5% completion, at least 99%completion, at least 99.5% completion, at least 99.9% completion,wherein completion is a term commonly used in the art to mean 100 minusthe mole percent of leftover acid end groups divided by non-acid endgroups.

[0278] In addressing the present invention, the first step preferablyoccurs in a pipe reactor. It is also preferred that the second step,which is performed after the first step, occur in the same or adifferent, second pipe reactor. However, as one skilled in the art willappreciate, the esterification step can occur using conventional priorart processes and then the polycondensation step can occur in a pipereactor of the present invention. Similarly, the esterification step canoccur using a pipe reactor of the present invention and thepolycondensation step can occur using a prior art process. According tothe present invention, at least one of the first or second steps occursin a pipe reactor.

[0279] Basic pipe reactor apparatuses as used herein are adapted asdisclosed herein from those known in the art for other applications andare typically based on standard pipes used in place of conventionalreactors. More generally, pipe reactors herein are typically an axiallyelongated, substantially cylindrically shaped apparatus, although shapesmay vary, such as square or rectangular, if not detrimental to thepurpose of the invention. In certain aspects herein, pipe reactors cansimply be hollow or empty or substantially hollow or empty pipe or tube.Hollow or empty, as defined herein, refers to the pipe or tube having noadditional devices or internal components, particularly no internalcomponents for mixing, transporting, or heating the reactor or ventfluids, such as agitators, static mixer elements, protruberences forcontrolling the fluid flow profile or mixing, packing, scrapers,rotating discs, such as, for example, those used in a wipe film or thinfilm reactor, baffles, trays, down comers, screws, or heating or coolingcoils, which are found in conventional reactors and in some pipereactors. Hollow or empty as used herein does allow for the placement offlow measuring devices, such as orifices, or flow control devices, suchas control valves or weirs, in the line. In one aspect of the invention,the pipe or tubes have a smooth interior surface. The pipe reactor ofthe present invention does not require surface area enhancementcomponents in the interior of the pipe nor does it require a filmforming enhancer as used in some of the pipe reactor designs of theprior art.

[0280] For the pipe reactors used in the first and/or second steps ofthe present invention, the criteria for choosing attributes are similarto the criteria generally considered when building a prior art,conventional reactor. For example, the designers may consider thecriteria of the desired capacity,. quality, agitation, heat transferarea, and disengagement. The designers may also consider informationdetermined from the operation and design of conventional reactors, suchas the working volume of the reactor, the heat transfer area, thesurface area of the liquid, the vapor piping velocity, the reactor vaporvelocity, the process flow rate into and out of the reactor, and theheat transfer media flow rate may also be considered. More specifically,the designers may determine the reactor volume from an existing reactor,a reactor design model, engineering calculations, or other sources ofdesign criteria. The length, l, of each pipe diameter required for eachzone of the reactor may be calculated using the reactor volume, V_(r),and the formula below:

[0281] l=V_(r)/(πr²), where r is the pipe radius.

[0282] The surface area, A, required for each zone may be calculated asfollows:

[0283] A=2*l*SQRT(r²−(r−h)²),

[0284] where h is the height of the liquid in the pipe and wherein r isgreater than h.

[0285] These calculations can be reiterated for each reaction zone,taking into consideration heat transfer area, vapor velocity (vapor flowin most standard reactors is vertical and in the pipe reactor willtypically be horizontal), and process flow rate. In this way, the lengthfor each pipe diameter can be determined. It should be appreciated thatnot all pipe diameters will meet the requirements of all reactorconditions. FIG. 3 contains an example of the calculations. Too small apipe size may create foaming problems in that foam may not break whereastoo big a pipe size may cause too great a pressure drop across the fluidheight. The reactor is not constrained to these design criteria as otherfactors may lead to a non-optimal cost design, such as materialavailability or sub optimization of an area of the reactor. In certainaspects, the pipe size is from 2 inches to 24 inches, preferably 6inches to 16 inches, more preferably 12 to 16 inches.

[0286] Reaction conditions (temperatures, pressures, flow rates, etc.)and materials charged to the reactor (reactants, coreactants,comonomers, additives, catalysts, etc.) can be those typically found inthe prior art for the commensurate polyester reaction, but the processof this invention allows even wider operating conditions than used inthe art. That is, the use of a pipe reactor in this present inventiondoes not necessarily require change in the reaction conditions ormaterials charged to the reactor per se. However, reaction conditionscan be different and, in fact, improved with the pipe reactor system ofthe present invention. In certain embodiments, pipe reactor conditionsare improved over the prior art reactor conditions, allowing enhancedperformance, such as higher purity product (e.g., lower DEG impurity) orimproved color.

[0287] One skilled in the art can determine such parameters based onprior art methods of making polyesters as a starting point. In oneaspect, the operating conditions in the prior art are a reactortemperature of 20-400° C., preferably above the melting point of thebulk of the fluid at any given point in the reactor train, pressure fromfull vacuum to 500 psig, a residence time up to about 8 hours, and amole ratio of from 1.005:1 to 6.00:1 on a basis of the mole ratio of theglycol residue to dicarboxylic acid residue, where the acid residue canbe based on the ester and the glycol residue can be based on a diol.These conditions or other prior art operating conditions can be easilymodified and optimized for the pipe reactor design of this invention byone of ordinary skill in the art after consideration of the disclosuresherein.

[0288] In addition to this general overview, considerations andattributes of the specific esterification and polycondensation pipereactors processes and apparatuses are discussed in more detail below aswell as certain other processes and apparatuses that may be usedtogether with or separate from the pipe reactor systems of the presentinvention.

The Esterification Step

[0289] With respect to the below discussion under this section ‘THEESTERIFICATION STEP,” including all subsections (Pressure Profile,Heating, etc.), unless specifically stated to the contrary, theprocesses and apparatuses of this invention discussed in this sectionbelow are equally applicable to, and can be used in, thepolycondensation processes and apparatuses.

[0290] As noted above, in one embodiment the first step involves use ofa pipe reactor to react the starting materials to form a monomer. In oneembodiment shown in FIG. 2, the pipe reactor 10 has an inlet 12, anoutlet 11, an exterior surface, and an interior surface. In one aspect,the interior surface of the pipe is circular, square or rectangular incross section, preferably circular, so as to form an inner diameter.

[0291] For both the esterification and polycondensation pipe reactors,the pipe reactor is preferably formed of a material that is non-reactivewith the materials flowing through the interior surface, including byway of example steel, iron, alloys, titanium, hastalloy, stainless,carbon steel, nickel, aluminum, copper, platinum, palladium, lithium,germanium, manganese, cobalt, zinc or a combination thereof. Othermaterials of construction include, but are not limited to, glass,ceramic, lined pipe, and plastics such asacrylonitrile-butadiene-styrene (ABS), polybutylene (PB), polyethylene(PE), poly vinyl chloride (PVC), chlorinated PVC (CPVC), polypropylene(PP), fiberglass, teflon, and a reinforced epoxy resin. Stainless steel,hastalloy and titanium are commonly used due to their properties,availabiliy and cost. For both ester exchange and polycondensation, acatalytic material may also be used for the pipe.

[0292] In use, the reactants typically are added into the pipe reactorproximal, or near, the inlet (i.e., closer to the inlet than the outlet)or adjacent to the inlet (right next to or at the inlet). As thereactants flow through the pipe reactor, the reactants react with eachother to form the monomer within the pipe reactor so that the formedmonomer exits from the outlet. However, not all of the reactants mustreact into the monomer while traversing from the inlet to the outlet(i.e., some of the reactants may exit the outlet without having reactedinto monomer) and still fall within the scope of the present invention.Additionally some of the monomer may react to form oligomer and stillfall within the scope of the present invention. The reactants added orinjected proximal or adjacent to the inlet of the pipe reactor may be inthe form of a liquid, gas, solid, or slurry, or other phase mixture.

[0293] It is easiest to add reactants as a liquid (e.g., EG and DMT)because the reactants may be independently pumped directly into theinlet of the pipe reactor or at another location upstream or downstreamof the inlet. In one particular design, one reactant may be added viathe inlet of the pipe reactor and another reactant added upstream of theinlet. In still another particular embodiment, one or more reactants maybe added through the inlet and another reactant may be added at one or aplurality of locations along the length of the pipe reactor between theinlet and outlet.

[0294] When the reactants are fluids, a pump can be used that dischargesthe reactants at a pressure above atmospheric pressure, typicallyproximal to the inlet of the pipe reactor. More specifically, a pump candischarge the reactants at a pressure sufficient for the materials totraverse through the pipe reactor and exit out of the outlet, whichinvolves overcoming frictional forces or losses, changes in potentialenergy (elevational head), and other forces that resist the flow of thematerials through the pipe reactor. The pump can be any pump known inthe art, nonlimiting examples of which include a centrifugal pump,including an in-line vertical centrifugal pump; positive displacementpump; power (piston); screw (double-end, single-end, timed, untimed);rotary (gear, multiple-rotary screw, circumferential piston, lore,rotary valve, or flexible member); jet (eductor single nozzle ormultiple nozzle); or elbow pump. The reactants can be pumped separatelyor mixed beforehand and pumped together.

[0295] Fluid reactants are easily pumped, either alone or mixedtogether, but solid reactants are more problematic. As discussed in moredetail below, the solid reactants can be added using a paste pump, a mixtank, a unique mix and feed system, a recirculation loop integrallyformed with the paste tank, or a combination of these apparatuses andmethods. Adequate mixing is needed to dissolve any solids present in theliquid, and to provide gas / liquid mixing to drive the esterificationreaction. Generally, it is preferred that the gas/liquid mixture is in abubble or froth state in the esterification reactor.

[0296] Pressure Profile

[0297] In the preferred embodiment, the pressure of the reactants at theinterior surface of the pipe reactor adjacent the inlet is higher, orgreater, than the pressure of the monomers and/or reactants at theinterior surface adjacent the outlet. To achieve this pressuredifferential, the inlet of the pipe reactor is preferably disposedelevationally below the outlet (as shown in FIG. 2) so that the pressuredifferential arises, in large part, from the hydrostatic pressureresulting from fluids contained within the interior surface of the pipereactor. That is, hydrostatic pressure exists between the downstream andupstream positions so that as the fluid flows upwardly through the pipereactor, the pressure decreases. The hydrostatic pressure is a functionof liquid density (temperature and composition), void fraction(reactants added, temperature, reaction by-products created, amount ofgas removed from the reactor), the height or elevational differencebetween two points in the pipe reactor, and the pressure drop due toflow in the pipe (flow rate, viscosity, pipe diameter).

[0298] The esterification pipe reactor can also take different shapes.For example, in one design (not shown), the pipe reactor issubstantially linear between the inlet and outlet so that the pipereactor is axially elongated. In another embodiment, the pipe reactor issubstantively non-linear. In another embodiment, the pipe reactor hasalternating linear and non-linear sections.

[0299] The pipe reactor can be essentially vertical, horizontal, or anyangle in between. The pipe reactor orientation can form any angle withthe vertical plane, from 0° (vertical, i.e. perpendicular to the groundor foundation) to 90° (horizontal or parallel to the horizon). Invarious aspects, the pipe reactor can be 0°, 10°, 20°, 45°, 60°, 75°,85°, 89°, or 90° with respect to the vertical pane. The pipe reactororientation angle with the vertical plane depends upon many conditions,particularly the product being made and the pressure profile desired.For example for PET production, if terephthalic acid is used, ahorizontal orientation is preferred, whereas if a DMT process is used, avertical orientation is preferred. For PETG, a vertical orientation ispreferred.

[0300] In various embodiments, the esterification pipe reactor can havea vertical configuration. In various embodiments for such a verticalconfiguration, the inlet of the pipe reactor can be positioned at least20, 50, 75, 80, 90, or 100 vertical feet below the outlet. In otherembodiments the inlet can be positioned from 20 to 200, from 50 to 200,from 50 to 175, from 90 to 150, or from 100 to 140 vertical feet belowthe outlet.

[0301] Another equally viable design includes a pipe reactor that isnon-linear between the inlet and outlet. One such design is shown inFIG. 2, in which the pipe reactor is serpentine in front plan view.Other profiles of the non-linear pipe reactor include, but are notlimited to, designs that are twisting; winding; twine; coil; contort;wreathe (move in a curve); convoluted; distorted; meandering; tortuous;sinuous; and/or labyrinth.

[0302] In another design, the pipe reactor proceeds from inlet to outletin a non-linear, horizontal run, and then proceeds vertically to afurther level with another non-linear horizontal run, and this processcan be repeated to any height (and width/length) desired. This creates apacked design with layered non-linear, horizontal runs.

[0303] In an alternative embodiment, the esterification (orpolycondensation) reactor can be a series of up and down vertical rises.Specifically, the esterification reactor (or polycondensation) would becomparable to FIG. 2 but rotated 90°. That is, with reference to FIG.16, the starting materials are pumped in at 12 and proceed verticallyupward and then vertically downward in an alternating pattern. Thisdesign allows the feeds to come in under pressure, then go to lowpressure, and then back to high pressure, alternating subsequently backand forth. The vapor could be removed at the low-pressure zone. Theeffluent exits at 11.

[0304] In these non-linear designs, the pipe reactor preferably includesa plurality of elbows disposed between the inlet and the outlet. Theelbows commonly form angles of forty-five (45) or ninety (90) degrees,but other angles are also contemplated. Each elbow changes the directionof flow within the pipe reactor as the reactants and/or monomertraverses through the elbow. The direction of the flow may changerelative to a stationary horizontal plane, such as the floor of thebuilding, or relative to a stationary vertical plane, such as a wall ofthe building, or relative to both stationary horizontal and verticalplanes. When the reactants and monomers flow through the elbows, moremixing advantageously occurs of the materials compared to a straightsection of the pipe reactor.

[0305] It is also contemplated to design the pipe reactor to obtain adesired pressure profile. As one skilled in the art will appreciate,when the reactants and/or monomer are in a liquid form, the pressure ofliquid is substantially constant when flowing along a portion of thepipe reactor that is horizontally oriented. That is, there is nohydrostatic pressure differential along a horizontal section of the pipereactor, but frictional losses occur as the liquids flow downstream thatmay vary the pressure along that horizontal section of the pipe reactor.In contrast, the pressure of the fluid decreases at an increasing rate,as that portion of the pipe reactor is oriented more vertically flowingdownstream.

[0306] Referring now to FIGS. 10 and 11, these engineering principlesmay be employed in embodiments of the present invention to createdesired pressure profiles for the reactants and/or monomer flowingthrough the pipe reactor. Profiles 21-25 of FIG. 11 correspond to views21-25 of FIG. 10. Changing the configuration of the pipe alters thepressure profile. FIGS. 10 and 11 are correct in principle, but inactuality, the pressure drop along the horizontal-pipes will onlydecrease by the frictional pressure drop along the length of the pipe.The vertical connections of the horizontal pipe segments will lead tonoticeable lower pressure in the pipe reactor. Accordingly, FIG. 11charting the pressure versus length or time would, in reality, occur insurges, not in the monatomic fashion depicted. Given this understandingof the simplified diagrams, each configuration will be described. View21 of FIG. 10 is a series of pipes equally spaced, which results in alinear pressure drop in the reactor assuming equal fluid density andvoid fraction. View 22 shows a pipe reactor with smaller pressure dropsat the beginning and larger pressure drops in the upper four, widelyspaced, reactor sections. The pipe reactor depicted in view 23 of FIG.10 has large initial pressure drops, caused by the increased verticalsections and smaller pressure drops in the last four sections of thereactor. View 24 shows a pipe reactor having four zones with smallpressure drop each and with a large pressure drop between each zone.View 25 design allows the reactor to drop the pressure in steps. Asalready noted, the pressure profiles for views 21 through 25 are showngraphically in FIG. 11 as profiles 21-25. It should be appreciated thatthe configurations described herein are illustrative only. Many otherconfigurations can be designed based on the principles discussed herein.

[0307] In another embodiment, it is contemplated having the inlet atapproximately the same elevational height as the outlet (i.e., the pipereactor oriented substantially horizontally) so that the pressure at theinlet will be greater than that of the outlet based on frictional lossesthat occur as the materials flow along the interior surface of the pipereactor. The pressure differential between the inlet and the outlet willnot be as great as the embodiment having the inlet elevationally higherthan the outlet. It is also within the scope of the present invention toorient the reactor pipe so that the inlet is disposed elevationallyabove the outlet.

[0308] The pressure in the top of the esterification reactor could beunder vacuum with the fluid traveling upward with the vacuum. In oneaspect, before the vacuum section, a vent can be used to remove the bulkof the water. In this embodiment, the first part of the polycondensationreactor could be placed on the top of the esterification reactor. Thiswould make the plant process smaller, with part of the polycondensationprocess/apparatus on the esterification side. In another embodiment, itwould also eliminate the longest seal leg in the facility. Additionally,in another aspect, a heat exchanger can be used in the reactor lineafter the vent.

[0309] Heating

[0310] Heating the reactants increases the reaction rate to facilitateforming the monomer and polycondensation. Accordingly, another optionalfeature of the present invention is to include a means for heating thereactants and/or monomers traversing through the pipe reactor. Moreover,heating the materials to boil along the interior surface of the pipereactor increases the mixing by (1) creating a buoyancy differentialbetween the gas/vapor formed by the boiling and the surrounding liquid(or solids) flowing along the pipe reactor and (2) breaking up theboundary layer created by frictional forces between the interior surfaceof the pipe reactor and the materials in contact with the interiorsurface. In various aspects, at least some of the fluids in theesterification process, the polycondensation process, or both theesterification and polycondensation processes are heated to boiling toprovide efficient mixing. In other aspects, at least some of the fluidscan be brought to boil by other means, such as, for example, by loweringthe system pressure or adding a component having a higher vapor pressurethan the fluids needing to be boiled. As one skilled in the art willappreciate, the highest heat transfer rate occurs for nucleate boiling(i.e., generation of individual bubbles or bubble columns), but othertypes of boiling are also contemplated.

[0311] The following chart provides the boiling point of exemplarycomponents that the present invention may process. Other components thanthose listed below may, of course, be used: Boiling Point TemperatureComponent ° C. Acetic Acid 118.5 Adipic Acid 330 Decomposing IsophthalicAcid (IPA) Sublimes Phosphoric Acid 213 Terephthalic Acid 301.4 Methanol64.5 1-Butanol 117.8 Isopropanol 82.5 Titanium Isopropoxide 82.5Titanium Dioxide greater than 475 Trimellitic Anhydride 390 Zinc Acetate100 Loses water then sublimes Antimony Oxide 1100 Cobaltous AcetateTetrahydrate 140 Dimethyl 1.4 Cyclohexanedicarboxylate 265 DimethylIsophthalate 282 Dimethyl Terephthalate (DMT) 288 Butanediol 230Cyclohexane Dimethanol (CHDM) 284-288 Diethylene Glycol (DEG) 245Ethylene Glycol (EG) 197 Triethylene Glycol 290

[0312] The heating means for the pipe reactor can take numerous forms.The pipe reactor may be heated by a variety of media through varioussurfaces. More preferably, the present invention includes heat transfermedia (“HTM”) that are in thermal communication with a portion of theexterior surface of the pipe reactor along at least a portion of thepipe reactor between its inlet and outlet. The heat transfer media cancircumscribe the entire outer diameter of the exterior surface andextend substantially the full length of the pipe reactor. Heat can alsobe added by inserting heat exchangers or by adding reactants hot or inthe vapor state. In one aspect, in a PET or PETG process, the ethyleneglycol and/or CHDM can be added hot or in the vapor state.Alternatively, induction heating or microwave heating may be used.

[0313] A heat exchanger can be used in a reactant feed line to heat orvaporize a reactant. A heat exchanger can also be used intermediate thepipe reactor, wherein the pipe reactor is in different sections and eacheffluent from one section is fed through a heat exchanger to heat thereactants and/or monomeric units. This heat exchanger intermediate thepipe reactor system is especially applicable if unjacketed pipe for thepipe reactor is utilized. Heater exchangers can be the low costcomponent of the reactor train depending upon the installed cost ofjacketed pipe vs. the installed cost of the heat exchangers. Typically,in the esterification and early polycondensation, the temperature of thefluid controls the residence time, so heat input can be the limitingdesign factor rather than the reaction kinetics. Therefore, to minimizevolume and costs, rapid heating can enhance the process. Heat exchangerscan be inserted at any location along the length of such as intermediatethe inlet and outlet or proximate or adjacent the inlet or outlet to theesterification reactor(s), the polycondensation reactor(s) or therecirculation loop or between any of the reactors (between theesterification reactors, polycondensation reactors, or between anesterification and polycondensation reactor), adjacent or proximate theinlet or outlet of any of the esterification or polycondensationreactors, or proximate, adjacent, or within any seal leg. Preferably, aheat exchanger is located at the start of each reactor section, wherethe pressure changes, since the vaporization cools the fluid. Therefore,as described below, insertion of a heat exchanger into, proximate, oradjacent the seal leg can be advantageous. If non-jacketed type pipe isused in esterification, then a low cost option is to use a heatexchanger at the beginning of the esterification process, and alsoutilize additional heat exchangers along the length of the reactor tobring the temperature back up as the by-product vaporizes. In oneaspect, the heat exchangers would be close together at the beginning ofthe esterification process and further apart later on, as the amount ofby-product vaporized is greater at the beginning of the esterification.

[0314] One example of the heat transfer media comprises a plurality ofelectrical heating components wrapped about the exterior surface of thepipe reactor. It is also contemplated using a jacket pipe circumscribingthe exterior surface, in which the jacket pipe has an inner surfacelarger than the exterior surface of the pipe reactor to form an annularspace therebetween. The heat transfer media, including by way of examplea liquid, vapor, steam, superheated water, compressed gases, condensingvapor gas, conveyed solids, electrical tracing, electrical heatingcomponents, or a combination thereof, are then located within theannular space. For use of a fluid heat transfer media (i.e., liquid,vapor, or steam), the annular space should be leak-tight in the lateraldirection so that the fluid flows longitudinally between the inlet andoutlet. More specifically, it is desired in this embodiment using fluidheat transfer media that the fluid flow within the annular space be in adirection counter to the direction of the material flowing through thepipe reactor (i.e., the heat transfer media flow from outlet to inletsince the reactants and monomer flow from inlet to outlet) althoughco-current HTM flow paths can also be used.

[0315] Based on the heat transfer media flow rate, the designers mustensure that the velocity of the heat transfer media in the annular spacebetween the process pipe and the jacket pipe is of the appropriatevelocity for good piping design. For the present application, a speed offrom approximately four to about eighteen feet/second linear velocity isgenerally considered appropriate. If the velocity is too high, then thejacket pipe diameter must be increased.

[0316] It is also contemplated that the heat transfer media may alsoflow or be located within the inner pipe and the process fluid locatedin the annular space between the outer surface of the inner pipe and theinterior of the exterior pipe. This design reduces the surface area ofthe process pipe and requires a larger external pipe, but may bebeneficial for some heat transfer media, such as high-pressure media.More area can be added with HTM both on the inside and the outside ofthe process fluid, with the process fluid in the middle annular space.

[0317] If more heat transfer is desired in a section of the reactor,then the surface area to process volume ratio must be increased. This isaccomplished by using smaller diameter process pipe. The smaller processpipe will increase the process linear velocity, but as long as the flowrate is not so high that it causes pipe erosion and is not in adisengaging section of the pipe reactor, this is acceptable. Thesehigher surface area zones will affect the cost of the pipe reactor. Ifthe process flow rate is too high, then multiple parallel pipes areused.

[0318] Degassing

[0319] While flowing from the inlet to the outlet, the reactants,monomers, oligomers, polymers, and by-products may form vapor or gasesas result of chemical reactions, heating, or other reasons. The presentinvention also optionally includes a means for removing vapors from thepipe reactor intermediate to its inlet and outlet and/or at, proximateor adjacent to the outlet. This removal helps to drive the reaction to afavorable equilibrium and/or to control the phase flow to the desiredregime. The removal locations can be, in certain aspects, at the end ofone or more or all zones (a “zone” referring to the esterification zoneand each polycondensation zone) and/or at one or more locations withineach reactor zone.

[0320] With reference to FIG. 20A, eight different flow regimes oftwo-phase flow in horizontal pipes are shown. Dark areas representsliquid and light areas the gas. In bubble flow, bubbles of gas movealong the upper part of the pipe at approximately the same velocity asthe liquid. In plug flow, alternate plugs of liquid and gas move alongthe upper part of the pipe. In stratified flow, liquid flows along thebottom of the pipe and gas flows above, over a smooth liquid/gasinterface. Wavy flow is similar to stratified flow except that the gasmoves at a higher velocity and the interface is disturbed by the wavestraveling in the direction of the flow. In slug flow, the roll wave ispicked up by the more rapidly moving gas to form a slug, which passesthrough the pipe at a velocity greater than the average liquid rate. Inannular flow, the liquid flows in a thin film around the inside wall ofthe pipe and the gas flows at a high velocity as a central core. Thesurface is neither symmetrical nor smooth, but rather is similar to rollwaves superimposed on squalls, as noted for wavy flow. In dispersed orspray flow, most of the liquid is entrained as spray by the gas. Thespray appears to be produced by the high-velocity gas ripping liquid offthe crests of the roll waves. Froth flow is similar to bubble flow onlywith larger bubbles or void percentage. See generally, Robert S.Brodkey, “The Phenomena of Fluid Motions,” Addison-Wesley Series inChemical Engineering, pp. 457-459, 1967.

[0321] For the esterification processes of this invention, froth orbubble flow in the pipe reactor is generally the optimum region tooperate in, as it provides good mixing of the vapor and liquid forfacilitating the reaction. For the polycondensation step of thisinvention, stratified flow in the pipe reactor is the optimum flowregime, as it provides good disengagement of the vapor by-product fromthe liquid product. Stratified flow is also the optimum flow for thevent off of the pipe reactor of this invention in either esterificationor polycondensation. FIG. 20B, which is a Baker Plot on a log-log scaleof By (in lb/(hr ft² ), a function of vapor mass velocity) versus Bx (afunction of the ratio of liquid to vapor mass velocities), shows thevarious, typical flow regimes of two-phase flow in horizontal pipes. .See generally, Baker Plots for two phase flow, e.g., in U.S. Pat. No.6,111,064, and in Perry's Chemical Engineers' Handbook, 6th ed, pgs.5-40 and 5-41, both hereby incorporated by reference for the indicatedpurpose. As stated above, froth or bubble is optimum for theesterification process, whereas stratified is the optimum for theprepolymer and finishing steps of the polycondensation process. Slug andplug flow risk possible equipment damage, annular and disbursed providetoo low a residence time, and wavy flow entrains process liquid into thegas stream, which causes fouling in the gas handling equipment.

[0322] In the early part of esterification, in certain embodiments, asolid can be present, which can create a three-phase flow. However, theoptimum flow regimes described above pertain to the relationship of theliquid and the gas. The solid does not, in fact, impact the gas/liquidflow regime, but it should be noted that for clarity, if a solid ispresent, it may not be a true two-phase flow since a third (solid) phasemay be present.

[0323] Movement between the fluid regimes is accomplished by changingplant capacity, increasing the recirculation rate, modifying therecirculation removal location in the process, venting off vapor,changing the pipe diameter, using parallel pipes, changing the physicalparameters by means such as temperature, pressure, composition, adding adiluent or an inert component, or by other means.

[0324] With reference to FIG. 20B, for the esterification process, tomove in the right-hand direction on the graph, the recirculation can beincreased in an amount or ratio to achieve the froth or bubble state. Tomove upward on the graph, smaller diameter pipe is used. To move left,additional paths are used. For the polycondensation process, if thevapor velocity is too high, then additional parallel pipes can be addedto decrease the vapor velocity, in order to achieve a stratifiedtwo-phase flow regime.

[0325]FIG. 24 shows one possible set of two-phase regimes for oneembodiment of the invention for a process for making PET homopolymer. Inthis embodiment, the esterification reactor starts at point 400 in thefroth or bubble regime and slowly moves towards point 401 as the processproceeds through the reactor. The velocity is lowered for disengagementof the two phases at point 402 in the stratified zone and then proceedsthrough the first pressure zone separator, for example, a seal leg, intothe first stage of polycondensation at point 403. The process proceedsalong the path to point 404 until the second pressure zone separator isreached moving the flow regime to point 405. The process proceeds alongthe path past point 406 to the last pressure zone separator. The lastpolycondensation zone is not shown as it is not on the scale for thisdiagram but has the same pattern as the first two zones.

[0326] Additionally, venting the gases from the system can control vaporflow and the ratio of liquid over vapor flow. Venting removes vapor.This moves the process down (less vapor flow) and to the right (higherratio of liquid to gas). The embodiments below show some methods thatmay be used to move in any direction on the graph to change flowregimes.

[0327] Entrained gases can be vented from a pumped liquid by controlledreduction of the flow velocity of the fluid in a degassing enclosurecoupled with controlled venting of collected gas from the degassingenclosure. More preferably, it has been found that gases entrained in apumped fluid stream can be separated from the pumped liquid byincorporating a length of degas piping in the flow path of the fluidstream and releasing the separated gases through such a standpipe, or aflow-controlled vent. As used herein, the term “entrained” and liketerms, refers to undissolved gas present in a fluid; for example, gas ina fluid in the form of bubbles, microbubbles, foam, froth or the like.

[0328] In one presently preferred embodiment, the vapor removing means,or degassing means, comprises a vent or venting mechanism incorporatedinto the pipe reactor. The venting mechanism is positioned so thateither all or a portion of the reactants and monomer traversing withinthe interior surface of the pipe reactor also flow through the ventingmechanism when flowing from the inlet to the outlet.

[0329] Referring now to FIGS. 7a-7 f, the venting mechanism functions toslow the velocity of the reactants and/or monomer in the pipe reactor toan extent sufficient to permit entrained gas to separate from the fluidreactants and/or monomer. The venting mechanism preferably produces alaminar, stratified, non-circular, two-phase gas/liquid flow. The extentof velocity reduction in the venting mechanism to provide the desiredtwo-phase (gas/liquid) flow can be determined by one of skill in the artusing (1a) the size of the gas bubbles likely present and the viscosityof the fluid, or (1b) the physical properties of both the liquid and thegas, and (2) the anticipated flow rate through the pipe reactor. Theinternal dimensions of the venting mechanism are selected to provide alarger cross-sectional area open to fluid transport than thecross-sectional area of the pipe reactor adjacent the venting mechanism.Based on mass flow rate principles, since the inner diameter increases,the velocity for a constant flow rate decreases. With the slowervelocity, the gases rise and come out of solution until the pressure ofthe released gases prevents additional gases from coming out ofsolution. Venting the released gases allows additional gases to come outof solution as the equilibrium originally existing between the gases insolution and out of solution is shifted.

[0330] For separation of entrained gases in the reactants and/or monomerdisclosed in the present disclosure, for example, it is desirable thatthe venting mechanism reduce the flow rate of the fluids flowingtherethrough and preferably a stratified two-phase flow regime isachieved in the venting and polycondensation process. The residence timeof the fluid within the venting mechanism is also controlled byappropriate selection of the length of the venting mechanism to allowsufficient time at the reduced velocity within the venting mechanism foradequate separation of entrained gas from the liquid. The appropriateresidence time for a particular fluid flow may be determined by one ofordinary skill in the art either experimentally or empirically afterconsideration of the disclosures herein.

[0331] For best results, the venting mechanism is disposed or orientedsubstantially horizontally so that the vapors and gases, within thereactants and monomer flowing therethrough flow substantiallyhorizontally and collect at the top area of the venting mechanism. Theattributes of a desirable venting mechanism allows the gases coming outof solution to be trapped by any design capable of allowing the liquidto pass on the bottom but restricting the flow of the gas on the top.

[0332] Several designs that can be used to disengage the gas from theliquid reactants and monomer include, but are not limited to, those inFIGS. 7a-7 f. Each embodiment in FIGS. 7a-7 f has an inlet 31 to receivethe fluid and gas/vapor mixture, a fluid outlet 32, a tee 36, and agas/vapor outlet 33. The venting mechanism can comprise an eccentricflat-on-bottom reducer(s) 37 to slow the velocity of the fluid into thestratified regime and to minimize the entrainment of the liquid into thevapor.

[0333] The reducer allows for a certain amount of surface area so thatthe vapor velocity on the liquid surface is sufficiently slow so thatthe vapor does not drag liquid along with it when it releases andsufficient liquid path cross-section area so that the linear velocity isslow enough that the vapor bubbles disengage from the liquid by buoyancydifferential that causes the two phases to separate. Reducers arepreferred where there is no limitation on pipe diameter or in reactorcapacity. If pipe diameters are limited and plant capacity is notlimited, an alternative to a reducer can be providing pipes and parallelto provide a lower linear velocity and more surface area in a shorterpath length.

[0334] The venting mechanism preferably has an effective inner diameter(or greater flow area) larger than the inner diameter of the pipereactor. Velocity can also be reduced by using multiple parallel pipesas shown in FIG. 7f. In one aspect, the system of FIG. 7f does not needa reducer on the inlet. The configuration in FIGS. 7e and 7 f can befurther enhanced with a weir at 38 that is in the top half of the pipe(inverted weir) between the TEEs 36 and the elbow to the right of theTEEs.

[0335] As the gases and vapors come out of solution within the ventingmechanism, they must be removed. To this end, the venting mechanismpreferably further comprises an upstanding degas stand pipe coupled tothe venting mechanism. The degas stand pipe has a receiving end in fluidcommunication with the venting mechanism and an opposed venting endpositioned elevationally above the inlet end. Although a straightembodiment is contemplated, it is preferred that the degas stand pipe benon-linear between the receiving end and the venting end.

[0336] In one embodiment, the vent further comprises an upstanding degasstand pipe coupled to the vent, wherein the degas stand pipe has areceiving end in fluid communication with the vent and an opposedventing end disposed vertically above the inlet end; and wherein thedegas stand pipe is non-linear extending in its lengthwise directionbetween the receiving end and the venting end thereof, and wherein thedegas stand pipe is formed of three contiguous sections each in fluidcommunication with each other, a first section adjacent the receivingend and extending substantially vertically from the vent, a secondsection coupled to the first section and oriented at an angle relativeto the first section in plan view, and a third section coupled to thesecond section and oriented at an angle relative to the second sectionin plan view so that the third section is oriented substantiallyhorizontally. In one aspect, the vent is a first section vertical pipecoupled to a third section horizontal pipe with a second section pipeconnecting the vertical and horizontal pipe at any angle other than 0 or90 degrees, preferably at a 45 degree angle. In various aspects,substantially vertical, with respect to the first section, includes, thefirst section being oriented at an angle of from about 0 to about 60degrees relative to the vertical plane, from about 0 to about 50 degreesrelative to the vertical plane, from about 0 to about 45 degreesrelative to the vertical plane, from about 0 to about 30 degreesrelative to the vertical plane, from about 0 to about 15 degreesrelative to the vertical plane, or about 0 degrees (vertical) to thevertical plane; the second section being oriented at an angle to thevertical plane of from about 5 to about 85 degrees, from about 15 toabout 75 degrees, from about 30 to about 60 degrees, or about 45degrees; and substantially horizontal, with respect to the thirdsection, includes being oriented at an angle relative to the horizontalplane of plus or minus from about 45 to about 0 degrees, plus or minusfrom about 30 to about 0 degrees, plus or minus from about 15 to about 0degrees, plus or minus from about 5 to about 0 degrees, or about 0degrees. Plus or minus with respect to the third section is intended tomean that the first and second sections are typically placed at an anglewith respect to the vertical such that the vapor or gas fluid flowingtherethrough proceeds in an upwardly direction (with the liquidinitially proceeding upwardly but then after full disengagement movingin a downwardly direction back to the process), whereas the thirdsection can be oriented in an upward, horizontal, or downwardorientation. In another aspect, the first section is oriented at fromabout a 0 to about a 60 degree angle relative to the vertical plane, thesecond section is oriented at from about a 5 to about an 85 degree anglerelative to the vertical plane, and the third section is oriented atfrom about a 0 to about a 45 degree angle relative to the horizontalplane. In another aspect, the first section is oriented at 0 degreesrelative to the vertical plane, the second section is oriented at 45degrees relative to the vertical plane, and the third section isoriented at 0 degrees relative to the horizontal plane. Preferably, thefirst section is oriented at about a 45 degree angle relative to thesecond section, and the third section is oriented at about a 45 degreeangle relative to the second section. Preferably, the third section isco-current to the process line that it is in fluid communication with,as shown in FIG. 7g, as would be shown if the device of FIG. 7g were tobe placed or transposed directly over FIGS. 7a-7 f where outlet 33connects to inlet 34, or as shown in FIG. 8 (assuming that the element137 is on the same plan view plane as TEE 36 or 139). However, the thirdsection can be countercurrent, or even a point between being co-currentand countercurrent. Countercurrent can provide for more efficientdisengagement but presents equipment layout disadvantages. Thus, thedegas standpipe creates a non-linear path from the first to the secondsection and then another non-linear path from the second section to thethird section. In another aspect, the third section is positioned at aminus 45 degree angle with respect to the horizontal, creating adownward flow path in the third section, and for this aspect, preferablythe third section is oriented at a 90 degree angle to the secondsection, which is preferably oriented at a 45 degree angle to thevertical plane. The vent is an extremely low cost configuration toperform a disengagement function, in that there are no moving parts inthe basic pipe design of the vent, and the vent can be merely emptypipe.

[0337] As shown in FIG. 7g and FIG. 8, the preferred embodiment of thedegas stand pipe is formed in three contiguous sections in fluidcommunication with each other: a first section adjacent the receivingend and extending substantially vertically from the venting mechanism; asecond section coupled to the first section and oriented at about aforty-five degree angle relative to the first section in plan view; anda third section coupled to the second section and oriented at about aforty-five degree angle relative to the second section in plan view sothat the third section is oriented substantially horizontally.

[0338] A common feature is that the standpipe is vertically oriented andthe venting mechanism is horizontally oriented, which creates anon-linear path from inlet to outlet and thus allows the gas to escapewithout the liquid also flowing out of the standpipe. With reference toFIG. 7g or FIG. 8, which venting mechanism arrangement is alsoapplicable to the esterification process, the pipe lengths 136 and 145are adjusted until a straight path from component 144 (or inlet 34 inFIG. 7g) to component 137 is not possible. Thus, no straight path existsbetween inlet 34 and exit 35. This non-linearity causes all or most ofthe liquid droplets in the vapor to impinge on some surface of the ventpiping. Thus, FIGS. 7a-7 f show six different vapor disengagementarrangements, embodiments of FIGS. 7d, 7 e, and 7 f being most preferredas they have no low spots that would be detrimental in a drainingoperation. In each embodiment of FIGS. 7a-7 f, the embodiment of FIG. 7ggas/vapor inlet 34 is placed in fluid communication with the outlet 33of venting “tee” 36 of FIGS. 7a-7 f, such that the vapor first proceedsthrough the vertical section of FIG. 7g, then through the diagonalsection then through the horizontal section, and exists the outlet 35.

[0339] It is also desirable to include a flow control device within thedegas standpipe to control the flow of fluids there through. The flowcontrol device may be, for example, an orifice; throttle valve; controlvalve; hand valve; reduced pipe section; outlet pressure control;nozzle; and/or bubble through liquid for head.

[0340] The flow control device preferably allows approximately ninetypercent of the vapor generated to this distance in the pipe reactor topass while the remaining ten percent is retained with the liquid. Thisapproximately ninety/ten percentage ratio ensures that liquid will notpass through the gas line and maintains the approximately ten percent ofthe gas for mixing in the pipe reactor. The amount of gas removed cannotapproach one hundred percent as a maximum, since the liquid would flowinto the standpipe along with the gases.

[0341] The venting end of the degas stand pipe is typically in fluidcommunication with a distillation system to which the vapors flow or areevacuated. It is also possible to vent the vapors to ambient. Thepressure at the venting end of the degas stand pipe can be controlledwhen the venting end is in communication with the distillation system,whereas when venting to ambient, the venting end will be at atmosphericpressure.

[0342] One skilled in the art will appreciate that the efficiency ofvapor removal can be improved by increasing the inner diameter of thepipe reactor adjacent and prior to the venting mechanism to maximize thesurface area of the liquid and minimize the vapor velocity at thesurface half of the pipe diameter. If the velocity in the pipe in thevicinity of disengagement is too high, the pipe diameter may be expandedas shown in, for example, FIG. 7d. In some embodiments, the expansionsections preferably have an eccentric flat-on-bottom reducer to keeppockets from forming in the reactor. These pockets reduce the reactionarea, thereby reducing capacity, and in cannot be readily drained duringthe process. The configurations shown in FIGS. 7d and 7 f do not trapliquid and allows complete draining on plant shutdowns. The ventingmechanism can be the same size; smaller or larger in diameter than theline it is attached to. In one aspect, the venting pipe is at least onestandard pipe size larger than the pipe being vented, in another aspect,is double the size of the pipe being vented. Because the typical optimumpipe size for the pipe reactor design herein is normally the largestpipe size available, and therefore it is not practical to have a ventingpipe being larger than the pipe being vented, multiple venting pipes tolower the velocity can be used as an alternative design as shown in FIG.7f.

[0343] If additional surface area is required or desired, additionalpipes may be installed at the same elevation, in which the additionalpipes run parallel to each other and all include a venting mechanism(see, for example, FIG. 7f). This series of parallel pipes and ventingmechanisms provide additional area for the disengagement of gas from thereactants and monomer.

[0344] One skilled in the art will appreciate that no gas removal isrequired to maintain the reaction within the pipe reactors, but removalof gas enhances the reaction rate by removing a limiting species. Thegas removal also reduces the void fraction making the final reactorvolume smaller.

[0345] One skilled in the art will further appreciate that multipleventing mechanisms can be used in the pipe reactor between its inlet andoutlet. For example, in one embodiment, the esterification orpolycondensation reactor has at least two sections of a first sectionand a second section, and wherein the pressure is reduced in thepolycondensation reactor, the reducing step comprising at least twodegassing mechanisms incorporated into the polycondensation reactor sothat the polycondensation fluids traversing within its inside surfacealso flow sequentially by the two respective degassing mechanisms whenflowing from the first end to the second end of the polycondensationreactor, and wherein the two degassing mechanisms are locatedrespectively at the first section and the second section of thepolycondensation reactor. In one aspect, the first and second sectionsof the esterification or polycondensation reactor are maintained atdifferent pressures from each other. In another embodiment, theesterification or polycondensation pipe reactor includes a top section,a middle section, and a bottom section, and each of the three sectionsincludes at least one venting mechanism. In a particular aspect, thepolycondensation reactor includes a top section, a middle section, and abottom section, and wherein the pressure is reduced in thepolycondensation reactor, the reducing step comprising at least threedegassing mechanisms incorporated into the polycondensation reactor sothat the polycondensation fluids traversing within its inside surfacealso flow sequentially by the three respective degassing mechanisms whenflowing from the first end to the second end of the polycondensationreactor, and wherein the three degassing mechanisms are locatedrespectively at the top section, the middle section, and the bottomsection of the polycondensation reactor. The top, the middle, and thebottom sections of the polycondensation reactor can be maintained atdifferent pressures from each other. Another design consideration is, asnoted above, including a plurality of elbows in the pipe reactor, whichcan assist in removing the vapors from the reactants and monomer. Morespecifically, the pipe reactor can include a first elbow disposedupstream of the venting mechanism and a second elbow disposed downstreamof the venting mechanism.

[0346] Addition of Reactants into the Pipe Reactor

[0347] The addition of reactants was addressed above in reference toadding fluid reactants into the pipe reactor using a pump. The presentsection discusses alternative methods of adding the reactants into thepipe reactor, including using a paste tank, a mixing tank, analternative feed system, and a recirculation loop.

[0348] One skilled in the art will appreciate that for each method thereactants may be added as discussed below, the reactants may be at thestandard transfer conditions or, alternatively and preferably, thereactants may be preheated before entering the reactor so that a cold,poor mixing zone does not occur. As one skilled in the art will alsoappreciate, adding cold reactants at locations upstream or downstreamfrom the inlet into the pipe reactor may be beneficial or necessary.

[0349] In some embodiments, external reactant lines for addition to thepipe reactor are preferably fed from the top down into the reactor, inwhich the entry location can be any location described herein or chosenby one skilled in the art. This reactant line should be jacketed at atemperature exceeding the melting point of the reactor contents at thelocation and the reactant feed point. Such a design keeps the reactantline from plugging when flow is stopped and (1) the control valve doesnot seal and (2) the check valve does not completely close, both ofwhich are common in prior art polyester plants.

[0350] Pumping Fluid Reactants

[0351] As discussed more thoroughly above, it is easiest to addreactants as a liquid (i.e., EG and DMT) because the reactants may bepumped directly into the inlet of the pipe reactor or at anotherlocation upstream of the inlet. The pump(s) discharge the reactantsabove atmospheric pressure proximal to the inlet of the pipe reactor.The reactants can be either pumped separately or mixed beforehand andthen pumped together.

[0352] Injection of Solid Materials Using a Paste Tank

[0353] The main goal of the esterification reactor is to completelyreact or convert the acids in the reactor to monomers and oligomers. Tomaintain this goal, solid acids, such as terephthalic acid, must be keptin the reactor until it dissolves. Paste tanks are frequently used toaid the mixing and blending, and U.S. Pat. No. 3,644,483 discloses theuse of such a paste addition. If a paste tank is desired, the paste ofany solid can be fed into the inlet of the pipe reactor or at anylocation along the path of the pipe reactor with or without therecirculation loop, which is described below.

[0354] Mix and Feed Tank System

[0355] Referring to FIG. 15A, the mix tank 41 is filled with the liquidto be added. Suitable liquids will dissolve or slurry with the selectedsolid. Suitable liquids include EG, methanol, CHDM and the like.Ethylene glycol will be used as an example in this section. The EG iseither heated or cooled to the appropriate temperature, depending on theadditive and the EG addition temperature, which is a function of ambientconditions and preconditioning. The heat exchanger 46, mix tank jacket,or internal coils, etc. is used to heat and cool the mix as it is beingrecirculated with pump 43 (not required when a mix tank jacket orinternal coils are used, but can be used to enhance heat and masstransfer) using temperature controller 45. The heat exchanger istypically supplied with steam 47 and water 48, but any appropriateheating and cooling media or mechanisms can be used. The additive isadded with agitator 44, pump 43 or both operating to suspend the solidsuntil they are dissolved into the EG. The level in the tank 42 ismonitored to control the addition of EG and to tell when the tank isempty for the next mix. Mix is pumped from the mix tank 41 to the feedtank 51 using pump 43 and going through a 3-way valve 60 or a pair of2-way control valves (not shown).

[0356] The feed tank 51 level 49 is controlled by adding mix from mixtank 41. When mix tank 41 is empty, the next mix is made while theresidual volume in feed tank 51 continues to feed the process. Pumps 52and 53 supply a feed header 59 to supply mix to the feed systems 57 and58 that control the additive flow into the process. The feed tanktemperature is controlled with temperature controller 54 using steam 55and water 56 or any appropriate temperature control media or mechanism.Agitator 50 is used to maintain a uniform mix in the feed tank.

[0357] Pumps 52 and 53 may be installed to directly feed the polymerline without using a header 59. At least one pump is required per linewith spares as appropriate.

[0358] An alternative system works as follows as shown in FIG. 15B. EGis added to unjacketed pipe 72, which acts as the tank in this system.The pipe 72 is located vertically in the plant, in an unused space orattached to an outside wall. The pipe 72 may have horizontal componentsto facilitate installation or enhancements to the volume, but theinstallation must not have traps for the solid being dissolved. Afterthe appropriate amount of EG is added to pipe 72 as monitored by level75, the circulating pump 74 is activated. The mix system temperature iscontrolled with temperature controller 77 with steam 78 and water 76 orany appropriate temperature control media or mechanism and in this caseuses a jacketed pipe 73. The additive is added and pump 74 circulationcontinues to suspend the solids in pipe 73 until the solids aredissolved. When the solids are dissolved, valve 60 is switched to directthe flow to feed tank 82.

[0359] Feed tank 82 should have the appropriate volume to allow a mix tobe made and dumped and a second mix to be made in case the first mix isin error. In one aspect, the inlet to tank 82 is just above the weldline of the bottom head. The overflow of feed tank 82 is preferably at adistance of 95% of the length of the tank between the tank head weldlines. The mix from pump 74 is directed through valve 60 into feed tank82 and overflows tank 82 back into pipe 72 of the mix system via pipe71. The flow of the mix via pump 74 through both the mix system and thefeed tank provides mixing and temperature control for both systemseliminating the need for temperature control, level control, and mixing(agitation) in tank 82. Mix is added to the plant through header 59 andsystems 57 and 58. In one aspect, no pumps are required since the tank82 is strategically located at an elevation that provides head pressureto the additive systems. As mix is consumed through stations 57 and 58(two station are shown, but 1 to a large number could be used), thelevel in pipe 72 will drop. When the level in pipe 72 is so low thatpump 74 starts to cavitate, valve 60 is switched directing flow frompipe 73 back to pipe 72 without going through tank 82. During this time,the level in tank 82 will start to decline. A new mix will be made inthe mix system starting with adding EG to pipe 72 as described above.The new mix is made and diverted through valve 60 into tank 82 beforetank 82 is emptied.

[0360] The pumps 74 for the mix tanks are located on a lower floor ofthe building. The mix tank pipe is positioned on the outside wall (orinside if space allows) to the roof, where the feed tanks 82 arelocated. The pipe 73 leaving the circulating pump 74 may be jacketed forheating or cooling. The return pipe to pipe 72 may also be jacketedwhere necessary or desirable. The top of the mix tank pipe 73 has athree-way valve 60 leading to the feed tank 82. The feed tank 82 has anoverflow line 71 back to the mix tank 72. The feed tank 82 has enoughresidence time between the overflow valve and the bottom of the feedtank to feed the plant, while the next mix batch is being made.Accordingly, and while the next batch is being made, the three-way valve60 is switched so that the fluid does not flow through the feed tank 82.This configuration eliminates all agitators and the level control in thefeed tank 82. As the feed tanks are located on the roof, the additiveflow pressure is derived from the elevation difference. Flow iscontrolled via a flow meter and a control valve in stations 57 and 58.This configuration also reduces space required in the facility.

[0361] For a typical system consuming 100 lbs/hr through each of 2 feedstations, the pipe 72 can be 14-inch schedule 10 pipe at a length of 72feet. The pump can be 50 gallons per minute and pipe 72 can be 3 or 4inches in diameter. Tank 82 in this case would hold 75 ft³ and haveapproximate dimensions of 3.5 feet in diameter and height.

[0362] The described fluid mixing and distribution system of theinvention thus includes a first elongate and vertically disposed fluidstorage vessel; a second fluid storage and dispensing vessel in fluidcommunication with the first vessel, the second vessel being disposed ata greater vertical elevation than the first vessel; a circulating pumpin fluid communication with the first vessel and the second vessel, thecirculating pump being constructed and arranged to pass a fluid flowthrough the system and to circulate the fluid from the first vessel intothe second vessel and from the first vessel to the first vessel; and acontrol valve in fluid communication with the circulating pump, thefirst vessel and the second vessel, respectively. The control valve isconstructed and arranged to selectively direct the fluid flow from thefirst vessel into the second vessel, and from the first vessel into thefirst vessel. The second vessel is in fluid communication with the plantprocess distribution system. A static pressure head formed by the fluidheld within the second vessel is used to pass the fluid from the secondvessel to the plant process distribution system.

[0363] Accordingly, an aspect of the invention is that the first vesselfurther comprises a fluid level monitor, the fluid level monitor beingconstructed and arranged to activate the control valve upon detecting apredetermined fluid level within the first vessel. In a furtheraspect,.both of or either one of the vessels is insulated. In anadditional aspect, the first vessel is temperature controlled, the fluidflow from the first vessel being used to control the temperature of thesecond vessel. The temperature controller further comprises a means forselectively adding steam and water to the fluid within the first vesselto raise and lower the temperature thereof, as desired. In anotheraspect, the second vessel further comprises a fluid inlet in fluidcommunication with the control valve such that the fluids are passedthrough the inlet and into the second vessel, and a fluid outlet spacedvertically above the inlet and in fluid communication with the firstvessel such that any excess fluids held in the second vessel overflowtherefrom into the first vessel. In yet another aspect, the fluid flowthrough the system is directed by the control valve from the firstvessel back into the first vessel until such time as the fluid withinthe first vessel has been mixed to a predetermined standard, and wherethe mixed fluid flow is selectively directed by the control valve fromthe first vessel into the second vessel.

[0364] An alternate embodiment of the system comprises a first fluidstorage vessel; a second fluid mixing and storage vessel; a circulatingpump in fluid communication with the first vessel and the second vessel,the circulating pump being constructed and arranged to circulate thefluid through the system and from the first vessel into the secondvessel; the second vessel being disposed at a greater vertical elevationthan both of the first vessel and the plant process distribution system;and a control valve in fluid communication with the circulating pump,the first vessel and the second vessel, respectively, the control valvebeing constructed and arranged to selectively direct the fluid flow fromthe first vessel back into the first vessel and from the first vesselinto the second vessel. The second vessel is in fluid communication withthe plant process distribution system, and a static pressure head formedby the fluid held within the second vessel is used to pass the fluidfrom the second vessel to the plant process distribution system.

[0365] The method of mixing and distribution a fluid within the fluidmixing and distribution system includes placing at least one fluid intoa first elongate and vertically disposed fluid storage vessel; passingthe fluid from the first vessel into a second elongate and verticallydisposed fluid mixing and storage vessel, the second fluid vessel beingdisposed at a greater vertical elevation than both of the first vesseland the plant process distribution system, with a circulating pump influid communication with the first vessel and the second vessel, thecirculating pump being constructed and arranged to pass the fluidthrough the system; using a control valve in fluid communication withthe circulating pump, the first vessel and the second vessel toselectively direct the fluid from the first vessel to either of thefirst vessel and the second vessel; and selectively passing the fluidfrom the second vessel to the plant process distribution system, thesecond vessel creating a static pressure head used to pass the fluidstored therein to the plant process distribution system.

[0366] Additional aspects of the method include adding at least onesolid or a second liquid to the at least one fluid within the firstvessel and mixing the combination therein; circulating the fluid throughthe first vessel until the materials therein are mixed with one another;passing the fluid from the first vessel into the second vessel once thematerials therein have been mixed with one another; controlling thetemperature of the fluid within the first vessel; controlling thetemperature of the fluid within the first vessel by selectively addingsteam and water to raise and lower the temperature thereof, as desired;measuring the fluid level within the first vessel with a fluid levelmonitor; the fluid level monitor activating the control valve upondetecting a predetermined fluid level within the first vessel; passingany overflow fluid from the second vessel back into the first vessel.

[0367] Injection of Reactants Using Recirculation

[0368] The present invention also optionally includes a means forrecirculating a portion of the reactants and monomer flowing though thepipe reactor. As noted above, the acid paste mix tank or the mix tankcan be replaced with a recirculation or recycle loop on the esterexchange pipe reactor.

[0369] In the presently preferred embodiment, the recirculating meanscomprises a recirculation loop having an influent and an effluent. Theinfluent is in fluid communication with the pipe reactor at any pointalong the esterification or polycondensation process, including, but notlimited to, proximal the esterification reactor inlet, proximal theoutlet of the esterification reactor, a point between the inlet and theoutlet of the esterification reactor, proximal the inlet to thepre-polymer reactor, proximal the outlet to the prepolymer reactor, apoint between the inlet and the outlet of the pre-polymer reactor,proximal the inlet or outlet to the polycondensation reactor, and at apoint between the inlet and the outlet of the polycondensation reactor,and the effluent is independently in fluid communication with the pipereactor at any point along the esterification or polycondensationprocess, including but not limited to, proximal the esterificationreactor inlet, proximal the outlet of the esterification reactor, apoint between the inlet and the outlet of the esterification reactor,proximal the inlet to the pre-polymer reactor, proximal the outlet tothe pre-polymer reactor, a point between the inlet and the outlet of thepre-polymer reactor, proximal the inlet or outlet to thepolycondensation reactor, and at a point between the inlet and outlet ofthe polycondensation reactor. In one aspect, the effluent is in fluidcommunication with the esterification pipe reactor proximal or adjacentits inlet, proximal or adjacent its outlet, or at a point between theinlet and the outlet of the esterification reactor. In one aspect, theeffluent from the recirculation is directed to the esterificationreactor proximate the inlet of the esterification reactor, in anotheraspect, the effluent is in fluid communication with the reactor adjacentthe inlet thereof, in another aspect, the effluent is in fluidcommunication with the reactor between the inlet and outlet thereof, inanother aspect, the effluent from the recirculation is directed to theesterification reactor upstream of the inlet of the esterificationreactor, in another aspect, the influent is in fluid communication withthe esterification reactor between the inlet and outlet thereof, inanother aspect, the influent is in fluid communication with theesterification reactor proximate the outlet thereof, in another aspect,the influent is in fluid communication with a second reactor, whereinthe second reactor is downstream of the esterification reactor, inanother aspect, the influent to the recirculation is in fluidcommunication with the polycondensation reactor, in another aspect, theinfluent to the recirculation is in fluid communication with thepolycondensation reactor proximate the outlet thereof, in anotheraspect, the recirculating step is performed using a recirculation loophaving an influent and an effluent, the effluent being in fluidcommunication with the pipe reactor proximal the inlet, wherein thefluids flowing through the recirculation loop are each recirculationfluids, in another aspect, the influent being in fluid communicationwith the pipe reactor between the inlet and outlet thereof or proximalthe outlet thereof. In this discussion, the reactants and monomer andany other fluid, such as oligomer and polymer flowing through therecirculation loop are referred to as the “recirculation fluids.”

[0370] As stated in another embodiment, the monomer can be provided tothe recirculation loop from the polycondensation reactor, which isdiscussed below. Thus, in this embodiment, the infeed to therecirculation loop is not from (or not solely from) the esterificationpipe reactor, to which the effluent of the recirculation loopdischarges.

[0371] In certain embodiments of the invention, which are shown in FIGS.13a and 13 b, the recirculation loop 91 includes a recirculation pump 92located intermediate its influent 93 and effluent 94 for increasingpressure of the recirculation fluids flowing therethrough. Therecirculation pump 92 is preferably an in-line centrifugal pump that islocated elevationally below the influent to obtain proper net positivesuction head (“NPSH”). This is because the recirculation fluids, asdiscussed in more detail below regarding the vapor removing means, areat or close to atmospheric pressure and the solution boiling point.Other pumps may alternatively be used, but a centrifugal pump is desiredbased on the pumping characteristics.

[0372] Once the recirculation fluids pass through the influent and therecirculation pump to increase the pressure, it may be desirable todecrease the pressure of the recirculation fluids, at least temporarily,at a location downstream from the recirculation pump. The advantage ofdecreasing the pressure is so that other materials, such as one or morereactants, can be drawn into the recirculation loop. The pressure ispreferably decreased using a pressure decreasing device, such as aneductor 95 through which at least a portion of the recirculation fluidsflow. The eductor pulls a slight vacuum, or sub-atmospheric pressure, atits throat. One skilled in the art will also appreciate that the eductor95 can be used interchangeably with a siphon; exhauster; venturi nozzle;jet; and/or injector or other like pressure reducing devices.

[0373] To feed or supply the reactants into the recirculation loop, afeeding conduit 96 is used that has a discharge end in fluidcommunication with the recirculation line adjacent the eductor. Thereactants to be fed are drawn into the recirculation line from thedecreased pressure of the recirculation fluids developed by the eductor.The feeding conduit also includes a receiving end, which is opposed tothe discharge end. The vacuum on the eductor throat keeps vapor fromlofting up into the solids being moved into the process line. The vaporwill condense on the solids and the mixture will be very sticky and plugthe system. The eductor expansion zone has intense mixing and separatesthe reactant, such as PTA, so that it does not lump in theesterification piping. The solid reactant may drag gas into the reactorwith it. This gas can be removed by another vapor disengagement systemafter the eductor. Alternately, a liquid feed to the reactor system canbe fed into the solid feed hopper. The liquid will displace the gas andthen the inerts will not enter the eductor.

[0374] A feeding system is used to meter and to feed selectively thesolid reactants or other components, such as modifiers, catalysts, etc.into the recirculation loop. One embodiment of a feed system is shown inFIGS. 13a and 13 b. The first component of the feeding system is a solidreactant storage device 97, such as a silo, dust collector, or bag houseused for storing the solid reactant to be fed into the recirculationloop. Liquid can be added to the solid reactor and storage device toreduce or eliminate the gas entrained with the solids. If a dustcollector is used, then a shipping unit on scales can meter in solids byweight and the shipping container acts as the inventory device.Additionally, the silo can act as the weight system and short terminventory. If solid raw material is conveyed from offsite, then noconvey system is required. A solid metering device 98, such as a rotaryair lock, a piston and valve (hopper), double valve, bucket conveyor,blow tank, or the like, is located at the bottom of the solid reactantstorage device 97 for receiving the reactants from the solid reactantstorage device 97. The next component of the feeding system is a loss inweight feeder (or volumetric feeder) 99 that is in communication withthe solid metering device 98, and also in communication with thereceiving end of the feeding conduit 96 and intermediate 96 and 98.Thus, the reactants are fed into the recirculation loop from the solidreactant storage device 97, to the solid metering device 98, into theloss in weight feeder 99, and then through the feeding conduit 96 to bedrawn into the recirculation loop adjacent or directly into the eductor95. The loss in weight feeder 99 can also be located at the solidreactant storage device 97 or at a feed tank (not shown) locatedupstream of 97 and which feeds 97. It will also be appreciated that theaddition of solid chemical components adjacent to a pressure decreasingdevice, such as an eductor, enables addition of solid chemicalcomponents directly into any reaction fluid found within a givenchemical manufacturing process. For example, in those embodimentsutilizing an eductor as the means for decreasing the pressure of therecirculation fluids, the vacuum on the eductor throat will keep vaporsfrom lofting up into the solids that are being introduced into theprocess line. Prior to the instant invention, vapors would condense onthe solids and the mixture would become very tacky, thus resulting inthe clogging of the entire system. However, in accordance with thepresent invention, the eductor expansion or divergence zone providesvery intense mixing and maintains sufficient separation of the solidcomponent, such as terephthalic acid, so that it does not lump in thevarious reactor zones. To this end, one of ordinary skill in the artwill appreciate that for best results, it is preferred to feed the solidcomponent directly into the pressure decreasing device, such as aneductor, at any point within the divergence or expansion zone of thepressure decreasing device.

[0375] The feeding system can feed more than one solid reactant. Also, aplurality of feeding systems can operate in parallel or series. In aspecific embodiment, the polymers can be made of multiple solids andthese can be fed individually each to its own pressure reducing devicein series or in parallel, or all of the polymer solids can be meteredinto one feed hopper into one pressure reducing device. The solidpolymer could also be metered together for entering the solid reactor todevice 97. This system can thus eliminate the need for a compressor andconvey system due to gravity flow.

[0376] In one aspect, the solid reactant storage device can be on weighcells to perform the function of the loss in weight feeder. Also,instead of using weigh cells as the loss of weight feeder, a belt feed,hopper weight scale, volumetric screw, mass flow hopper, coriolis flowmeter, hopper or feed bin weight loss, or the like can be used.

[0377] When the reactants added into the recirculating loop flow to theeffluent of the recirculation loop, the reactants and the otherrecirculation fluids re-enter the pipe reactor 101 adjacent or proximalthe inlet 100. Thus, this process of adding the reactants in therecirculation loop so that the reactants start near the inlet andtraverse toward the outlet perform the function of adding at least onetype of reactant into the inlet of the pipe reactor, which is one of theinitial steps in the process of the present invention. It isadvantageous to feed a solid reactant into the recirculation loop viathe feeding system so that the solid reactant is dissolved by therecirculation fluids, especially the monomer or oligomer, before flowingto the effluent of the recirculation loop.

[0378] It is also contemplated adding additional fluid reactants intothe recirculation loop. The fluid reactants may be added to assist thesolid reactants in dissolving in the recirculation fluids beforereaching the effluent of the recirculation loop, or as a convenience sothat the additional reactant does not need to be added separately at theinlet of the pipe reactor.

[0379] The fluid reactants are preferably added into the recirculationloop upstream of the eductor (before the addition point of the solidreactants), although the fluid reactants may likewise be addeddownstream of the eductor. It is contemplated adding the fluid reactantinto the recirculation loop through the recirculation pump 92 seal.Reactants can also be added upstream of the recirculation pump 92. Whenthe solid reactants are added through the feed system and the fluidreactants are also added into the recirculation loop, these processesresult in adding at least two types of reactants into the pipe reactorproximal its inlet into which the effluent of the recirculation loopfeeds.

[0380] The dissolution of the solid reactant material can be enhanced byincreasing the temperature and by changing the ratio of the polyestermonomer to solid reactant in the recirculation system, changing the feedmole ratio, and/or changing the pressure of the system.

[0381] Taking a specific example, one type of reactant fed into therecirculation loop via the feeding system can be PTA, which is a solidat room temperature. The recirculation design avoids use of a paste tankand inherent problems therewith. The fluid reactant can be, for example,ethylene glycol. Thus, if EG and PTA are the only reactants to be addedto form the monomer, then the effluent can feed directly into the inletof the pipe reactor as the only source of reactants added to the pipereactor. Of course, variations of this design are contemplated, such aspumping more of the EG reactant into the inlet of the pipe reactor, inaddition to the EG and PTA added proximal to the inlet of the pipereactor from the recirculation loop. In a separate aspect, the diol,such as EG, can be fed through the recirculation line before or afterthe recirculation loop pump or before or after the PTA feed line to therecirculation line, or upstream of but adjacent to the pressure reducingdevice along with the PTA feed.

[0382] In FIG. 13a, one embodiment is shown where the effluent from theend of the esterification process is teed off 106 and one portion of theeffluent is sent to the recirculation loop. In a separate embodiment, asshown in FIG. 13b, the tee 106 is intermediate the completeesterification process pipe reactors 101 and 102, so that the influentfor the recirculation loop is not from the end of the esterificationprocess, but rather comes from an intermediate point in theesterification process. In FIGS. 13a and 13 b, the final effluent fromthe esterification process is at line 103 (after vapor removal in line104).

[0383] In another embodiment, the effluent of the recirculation loop islocated downstream of the inlet of the pipe reactor. This embodiment ispreferable when the monomer that enters the influent of therecirculation loop or the slurry formed as a result of the addition atthe feeding station requires a shorter residence time than would occurif the effluent fed directly into the inlet of the pipe reactor.

[0384] In various embodiments, the influent to the recirculation loop isfrom either the esterification process or the polycondensation process.Specifically, in various aspects, the influent to the recirculation loopcan be from a point intermediate the esterification reactor (as shown inFIG. 13b), the end of the esterification reactor (as shown in FIG. 13a),the product from the outlet of the prepolymer reactor, the product fromthe outlet of the finisher reactor, or any point from the beginning ofthe esterification process to the final product from the outlet of thepolycondensation process. Thus, the recirculation fluids comprise invarious aspects the reactants, the polyester monomer, the polyesteroligomer, and/or the polyester polymer, depending upon where theinfluent from the recirculation loop originates. The recirculationsystem is not limited to the use of one recirculation loop, butalternatively comprises two or more recirculation loops configured inseries, parallel, or a combination thereof.

[0385] It is also contemplated for the recirculation loop that itincludes other features discussed above for the pipe reactor, such as aheating means and a vapor removing means for the recirculation loop,which may be the same components and apparatuses discussed above andencompassing the same features and embodiments. If monomer is removedfrom adjacent the outlet of the pipe reactor a shown in FIG. 13a, thenthe vapor removing means does not have to be added to the recirculationloop. Otherwise, the liquid elevation is raised or lowered until thepressure is near atmospheric and the vapor is removed to thedistillation system.

[0386] Addressing the vapor removing means specifically, in oneembodiment of the recirculation loop, the design is similar to thatdescribed above for the pipe reactor as shown in, for example, FIGS.7a-g. Also, although not required, it is preferable that the ventingmechanism be located proximal to the influent of the recirculation loopso that the vapors are removed prior to the addition of the reactants,and such a design is shown in FIG. 13a and 13 b at 104 in FIG. 13a and105 in FIG. 13b.

[0387] Of note, although there are advantages with the recirculationloop that will be apparent to one skilled in the art based on thediscussion above, it is not necessary to include the recirculation loopfor a pipe reactor to fall within the scope of the present invention.Instead, the components originally discussed, such as a pump for thefluid reactants and a paste mix tank for the solid reactants can beused. This embodiment using the recirculation loop, however, allows thedesigner to replace the paste mix tank, pump, instrumentation, agitator,etc. with a pump anda pressure reducing device, such as an eductor.

[0388] One skilled in the art will also appreciate that therecirculation loop is most advantageous for injecting solid reactantsand is less advantageous when only fluid reactants are added (e.g.,forming PET monomer from DMT and EG). Using a recirculation loop todissolve solid reactants reduces the abrasion caused by the solids inthe system. For example, solid PTA can be dissolved by the monomer inthe recirculation loop, rather than using a conventional paste tank. Ina conventional paste tank process, solid PTA is fed to the process andremains an abrasive component in the undissolved state. In fact, pipereactors that process only fluid reactants may not benefit from theadded complexity of including the recirculation loop. However, therecirculation loop can enhance the heat transfer to the esterificationprocess.

[0389] Weirs

[0390] A means may be included to control the level at the top of theesterification pipe reactor. In one embodiment, at least one weir isattached to the interior surface of the esterification pipe reactor andwherein the esterification fluids flow over the weir. As illustrated inFIG. 4, the desired controlling means is a weir 110. The weir ispreferably disposed proximal to the outlet of the pipe reactor.

[0391] The weir has a body portion circumscribed by an edge. A portionof the edge is referred to as the connecting edge and a remainingportion of the edge is the top edge. The connecting edge is of a size tobe complementarily received by a portion of the interior surface of thepipe reactor and attached thereto. Thus, since the interior surface iscircular in cross-section in the preferred embodiment, the connectingedge is also circular to complementarily contact and engage the interiorsurface.

[0392] Referring still to FIG. 4, the reactants and/or monomer is shownflowing from point 111 and over the weir at point 112. The weir acts asa barrier for the reactants and/or monomer so that the fluid materialflows over the top edge of the weir. Thus, the weir controls the liquiddepth along with the fluid viscosity, the flow rate, and the length ofthe pipe before the weir. After passing over the weir, the fluid flowsout of the outlet of the pipe reactor at 113. The weir, as describedbelow, may also have openings in it or at the bottom to provide flowuniformity and complete draining. This would include weirs with the topsloped, V-notched in the weirs, etc. The weir is preferably located adistance five to ten pipe diameters from the outlet of the pipe reactor.In one aspect, by sloping the top of the weir, the weir can compensatefor higher and lower flows and viscosities.

[0393] In alternative embodiments, the level can be controlled by anylevel controller known in the art, such as, but not limited to, acontrol valve, seal legs, level devices such as those that usedifferential pressure, radiation, ultrasonics, capacitance, or sightglasses. Other specific examples of level devices can be found inPerry's Chemical Engineer's Handbook, 7^(th) ed., p. 8-49, which ishereby incorporated by this reference.

[0394] Additives

[0395] Another optional aspect of the present invention comprises ameans for introducing one or more additives into the pipe reactorbetween its inlet and outlet. Such additives are described above andinclude, but are not limited to one or more of a catalyst, colorant,toner, pigment, carbon black, glass fiber, filler, impact modifier,antioxidant, stabilizer, flame retardant, reheat aid, acetaldehydereducing compound, oxygen scavenging compound, UV absorbing compound,barrier improving additive, such as platelet particles, black ironoxide, comonomers, mixtures thereof, and the like. Additives can be asolid, liquid, or gas. The additives can be preheated before entry tothe system, including a phase change, such as heating EG liquid to thevapor state to provide heat for the reactor.

[0396] In the preferred embodiments shown in FIGS. 12a and 12 b, theintroducing means comprises a sealable channel, as represented by any ofthe arrows in FIGS. 12a and 12 b, through the pipe reactor allowingfluid communication between its exterior surface and its interiorsurface and an injector for injecting the additive into the materialflowing within the pipe reactor (i.e., the reactants and/or monomer).The injector can include a pump or other means such as pre-pressurized,elevational, or gravity driven injection that injects the additive intothe interior of the pipe reactor, which must be performed at a pressuregreater than that of the materials within the pipe reactor at thelocation of the sealable channel.

[0397] The term “sealable channel” is meant to encompass any openingthat allows communication from outside the pipe reactor into itsinterior. It is preferred that the “sealable channel” be able to beclosed off so that when the additive is not being injected into the pipereactor, the reactants and/or monomer do not leak out of the pipereactor. The sealable channel may be “sealed” by a plug or the like, aswell as the injector not allowing leakage out of the pipe reactor.

[0398] The additives can be introduced or injected at any point alongany portion of the pipe reactor, as shown in FIGS. 12a and 12 b.Examples of suitable addition points include the sealable channeltraversing through a portion of the top, side, or bottom of thehorizontally oriented sections of the pipe reactor, the top, side, orbottom of a respective elbow, into a seal leg, and before a heatexchanger. As shown in FIG. 12b, injection into the elbow isadvantageous because of the resulting maximum mixing and quickincorporation of the additive into the reactants and/or monomer withouthigh-concentration eddies occurring inside of the pipe reactor.

[0399] Another aspect of the injecting means is including a nozzle atthe discharge or outlet of the injector. The nozzle can direct flowwithin the pipe reactor at the location of the sealable channel. Forexample, the nozzle can inject the additive co-current, counter current,or perpendicular to the reactants and/or monomer that are flowing withinthe pipe reactor at that location.

[0400] Returning to the design of the esterification pipe reactor, thepipe elevational height, pipe diameter, total length of pipe, andpressure at the inlet and outlet can vary widely depending upon theproducts made, plant capacity, and operating conditions. One of ordinaryskill in the art could readily determine these parameters using basicengineering design principles together with the disclosures herein.

The Polycondensation Step

[0401] With respect to the below discussion under this section, “THEPOLYCONDENSATION STEP,” unless specifically stated to the contrary, theprocesses and apparatuses of this invention discussed in this sectionbelow are equally applicable to, and can be used in, the esterificationprocesses and apparatuses.

[0402] As noted in the “Overview” section above, the second step of theprocess of the present invention is the polycondensation step, which inone embodiment occurs in the polycondensation pipe reactor. Thepolycondensation step involves reacting the monomers into oligomers andthen into the polyester polymer. The monomers may be provided from thefirst step in an esterification reactor, as discussed above, or from aprior art process. Alternatively, if oligomers were substantially formedin a prepolymer first step, then oligomers are reacted directly to formthe polymer.

[0403] In a specific embodiment, when PET polymer is formed, the PETmonomers are fed to the polycondensation pipe reactor. The PET monomersare reacted in the polycondensation pipe reactor to form the PEToligomer and then are further reacted preferably within the samepolycondensation pipe reactor to form the PET polymer. As used hereinwith respect to PET, monomers have less than 3 chain lengths, oligomershave from about 7 to about 50 chain lengths (components with a chainlength of 4 to 6 units can be considered monomer or oligomer), andpolymers have greater than about 50 chain lengths. A dimer, for example,EG-TA-EG-TA-EG, has a chain length of 2 and a trimer 3 and so on. Thus,the condensation pipe reactor of the present invention can take theplace of both a prepolymer reactor as well as a finisher reactor asthose terms are used in the prior art and as defined hereinabove.

[0404]FIG. 4 shows the output of the pipe reactor traversing over aweir, for level control, and into the polycondensation reactor of thesecond step of the present invention. Also referring to FIGS. 4 and 6,one skilled in the art will appreciate that pressure-restricting devices(such as, but not limited to a valve, orifice, or the like) between theesterification or ester exchange reactors and the polycondensationreactors can be used but are not required.

[0405] In one embodiment, a seal leg is used between theesterification/ester exchange reactor and the polycondensation reactor.Seal legs can also be used between some or all of the polycondensationstages. As was discussed above with respect to the esterificationprocess for the polycondensation process, a heat exchanger can be placedproximate or adjacent to, or even within a seal leg, therebytransferring heat to the fluid between the esterification andpolycondensation or between the polycondensation stages or zones.

[0406] The static equivalent to a seal leg is a barometer. Thedifference in pressure between two zones of the reactor is maintainedwith a fluid in a ‘U’ shaped pipe. The differential in pressure will beequivalent to the product of the fluid height times the density on thelow pressure side minus the fluid height times the density on the highpressure side. One skilled in the art will recognize that if thedifferential height is not great enough, the differential pressurebetween the zones will push the fluid out of the seal leg and both zoneswill assume-an equilibrium pressure. This can require the height of theseal leg to be very large between zones with high pressure difference.In addition, the side of the seal leg on the low pressure side willgenerally be boiling at the reduced pressure, hence the low pressureside's density will be reduced by the void fraction of the vapor.

[0407] Fortunately, the seal leg is a dynamic barometric device in thatthe fluid is flowing through the seal leg. This fluid flow hasassociated pressure drop with it and can be used to enhance the pressuredrop of the low pressure side. By adding a flow path restriction, suchas an orifice, valve, or small diameter piping, to the low pressure legof the seal leg, the pressure drop on the low pressure side per unit ofelevation can be increased. If the flow restriction is inserted beforethe heat is transferred into the seal leg, then the fluid will not betwo phases and the density of will be greater. Using these methods toincrease the pressure drop of the low pressure seal leg will decreasethe total height of the seal leg.

[0408] The present invention involves providing a polycondensationreactor having a first end, a second end, and an inside surface definingan inner diameter. The first end can be disposed elevationally above thesecond end so that gravity moves the monomer and any formed oligomer andpolymer from the first end to the second end.

[0409] As shown in FIG. 2, the polycondensation reactor can beserpentine in front plan view (but flow is in the opposed direction ascompared to the esterification pipe reactor—that is, the influent is at11 and the effluent is at 12 for the polycondensation process).Nonetheless, as with the esterification pipe reactor, other profiles,such as the designs hereinbefore described with respect to theesterification pipe reactor, are contemplated in addition to theserpentine design. It is also preferred to include a plurality ofelbows, each elbow changing the direction of fluid flow within thepolycondensation reactor. The materials used to form thepolycondensation reactor may also be the same as those used to form theesterification pipe reactor.

[0410] Thus, the monomer, which is preferably in a fluid form, isdirected into the first end of the polycondensation reactor so that themonomer flows downwardly through the polycondensation reactor. Themonomer reacts to form the oligomer and then the final polymer withinthe polycondensation reactor so that the polymer exits from the secondend thereof. As one skilled in the art will appreciate, not all of themonomer and/or oligomer must react to be within the scope of the presentinvention. The monomer, oligomer, and/or polyester polymer flowingthrough the polycondensation reactor are referred to as thepolycondensation fluids.

[0411] It is also preferred that the polycondensation reactor isnon-linear between the first end and the second end to improve the masstransfer/mixing of the monomer and formed oligomer and polymer. Ingeneral and as discussed below, the polycondensation mass transfer isaccomplished by the mass transfer at the surface of the oligomer (lowmolecular weight polymer) and by the foaming action of the gas evolvingfrom within the polymer. This gas is evolved from the heating at thewall surface and the reaction within the polymer. The mass transfer isfurther enhanced as the liquid falls over optional weirs in each sectionof the reactor. The reactor can be constructed without thepolycondensation reactor weirs if the physical parameters of the polymerallows.

[0412] The polycondensation reactor can be formed as a plurality ofcontiguous interconnected sections, in which the monomer, oligomerand/or polymer flows through the inside surface of each sectiontraversing from the first end to the second end of the polycondensationreactor. Adjacent sections of the reactor preferably form non-linearangles with each other.

[0413] The polycondensation reactor preferably forms an angle with avertically-oriented plane, in which the angle is greater than zerodegrees. Stated differently, each section is not parallel to thevertically-oriented reference plane and, thus, is not verticallyoriented. More specifically, the angle that each section forms with thevertically-oriented plane is between about I (almost verticallyoriented) and 90 degrees (horizontally oriented). The preferred angleprogresses from horizontal (90 degrees) to within about 26 degrees ofvertical; however, one skilled in the art will appreciate that thepreferred angle is based on viscosity and line rate (flow) within thepolycondensation reactor. Preferably, the sections can have differentangles relative to each other, preferably the initial sections having ahorizontal or near horizontal angle, and as the polycondensationreaction progresses and the fluid increases in viscosity, the angleincreases to provide an increased vertical sloping to facilitatetransport of the fluid through the polycondensation pipe reactor.

[0414] In one aspect, the polycondensation reaction at the top end has alow slope (more horizontal) because the fluid is of a low viscosity,whereas the bottom end is of a high slope (more vertical) because thefluid is of a high viscosity. The slope can be varied depending uponparameters such as viscosity and density of the fluid to achieve theoptimum effect. In another aspect, no slope is used in a horizontalconfiguration for the polycondensation reactor.

[0415] In one aspect, the polycondendation reactor has a generalhorizontal orientation rather than a vertical orientation. Thishorizontal orientation can include some vertical height to allow thepolycondensation fluids to flow by gravity in a downward mannerthroughout the system. In various aspect, for the horizontalconfigurations, the pipe reactor can have a length of at least 10 feet,at least 20 feet, at least 30 feet, at least 40 feet, at least 50 feet,at least 60 feet, at least 100 feet, or at least 200 feet. In otheraspects the length is from 10 to 500 feet, 20 to 250 feet, 50 to 200feet, 60 to 100 feet, or 60 to 80 feet. The upper length limit is onlylimited by the practical amount of horizontal space available at theproduction facility. In one embodiment, a pipe reactor of at least about60 feet is used because standard maximum length commercial pipe is about60 feet. Pipe reactors herein can even be hundreds of feet long or more.

[0416] In one aspect, the interior surface of the polycondensation pipereactor is circular, square, or rectangular in cross section, preferablycircular, so as to form an inner diameter.

[0417] To aid in the mass transfer/mixing, the present invention furthercomprises a means for heating the oligomer and polymer flowing throughthe polycondensation reactor. The preferred heating means is the same asdiscussed for the esterification pipe reactor of the first step, namely,heat transfer media in thermal communication with a portion of theoutside surface of the polycondensation reactor along at least a portionof the polycondensation reactor between the first and second endsthereof or heat exchangers in series with jacketed or unjacketed pipe.In the preferred embodiment, the heat transfer media are the same asdiscussed above. In one aspect, heat exchanges can be used, preferablybetween the polycondensation zones. In a particular embodiment, heatexchangers are used in conjunction with seal legs, such as by providingthe heat exchangers proximate, adjacent, or within the seal legs used toseparate the zones.

[0418] Also similar to the esterification pipe reactor discussed above,in one aspect, the polycondensation reactor of the present inventionfurther comprises at least one weir attached to the inside surfacethereof. The polycondensation fluids flow over the weir. The weir actsas a barrier for the monomer/oligomer/polymer so that it flows over thetop edge of the weir when flowing from the first end to the second endof the polycondensation reactor. The weirs can be the same weir designand/or configuration described above in the esterification section. Inone aspect, a weir is used between each zone of the polycondensationreactors, and in another aspect, a weir is used between some of thezones of the polycondensation reactors but not in all zones.

[0419] The weir controls the liquid level in each pipe level of thereactor. These weirs can be as simple as a half circle or include addedcomplexities. In one aspect, by sloping the top of the weir, the weircan compensate for higher and lower flows and viscosities. In oneaspect, the design of the polycondensation pipe reactor allows theintegration of any weir design to compensate for these factors. It isalso contemplated including at least one opening though the body portionof the respective weirs so that the monomer/oligomer/polymer flowsthrough the opening, as well as over the top edge of the weir whenflowing thereby. These openings or holes in the weirs improve the flowand reduce stagnant flow zones. In still another embodiment, a sectionof the body portion of the weir may be detachably removable to allow afluid to pass through that section of the weir instead of over the weir.For example, the section may be a “V” notch or “V-slot” in the weir. The“V-slot” in the middle of each weir from the inside of the pipe to thecenter of the pipe further allows the reactor to drain when shutdown.These designs increase the mixing of the fluids when traversing by theweir.

[0420] The first pipe in each zone can be horizontal and can befunctional without a weir, but the weir has the advantage of increasingthe efficiency of the system by both surface area and residence time.Additionally, the polycondensation pipe can be sloped downward,particularly for when the IV of the fluid approaches 0.5 dl/g orgreater.

[0421] Another aspect of the present invention that is similar to theesterification pipe reactor discussed above is that the polycondensationreactor preferably also includes a means for reducing the vapor pressurein the polycondensation reactor, such as a degassing mechanism in fluidcommunication with the inside surface of the polycondensation reactor.

[0422] Similarly, the degassing mechanism used in the polycondensationreactor may include a venting means and/or stand pipe similar to thedesign discussed above in the esterification section. Of note, theventing end of the degas stand pipe is preferably in fluid communicationwith a vacuum source so that a sub-atmospheric pressure exists in thestandpipe and at the inside surface of the polycondensation reactor. Thevacuum source may be maintained by vacuum pumps, eductors, ejectors, orsimilar equipment known in the art. The vacuum in each of the vaporremoval lines can be used to control the pressure in the zones of thepolycondensation reactor.

[0423] Referring now to FIG. 9, which shows one embodiment of theweir/degassing system, specifically, using an optional flow invertersystem for the separated liquid, the polycondensation reactor may alsoinclude a reducer 123 located immediately downstream of a weir 124inside tee 128. In one embodiment, at least one polycondensation fluidflows through a flow inverter, wherein the flow inverter is proximate toand downstream of the weir. The reducer has a diameter smaller than theinner diameter of the polycondensation reactor and the reducer forms apart of the juncture of two interconnected sections, in which theinterconnected sections are formed by an upstream section and adownstream section. The reducer is connected to the upstream section andextends into the downstream section. The reducer has a lower end 127having an aperture through which the monomer/oligomer/polymer flows whentraversing from the upstream section to the downstream section. Thelower end of the reducer 127 is spaced apart from the inside surface ofthe downstream section, which improves mixing as the fluids fall fromthe force of gravity into the inside surface of the downstream section.In fact, it is more preferred that the lower end of the reducer bespaced apart from a top or upper surface of the monomer/oligomer flowingthrough the downstream section that the fluid flowing through thereducer splatters upon the top or upper surface of themonomer/oligomer/polymer.

[0424] Stated differently and still referring to FIG. 9, in oneembodiment, the inside and outside flow paths can be mixed by using aflow inverter. By dropping over the weir 124 and into a reducer 123before entering the next elbow 125, the liquid monomer/oligomer/polymerwill be mixed from inside out and vice versa. The liquid flows in thepipe from the left 120 and passes over the weir 124, which controls theliquid depth. The vapor continues out the right side of the tee 128 at121. The degassed liquid flows into the concentric reducer 123. Theconcentric reducer 123 passes through a pipe cap 126 of a largerdiameter pipe. The reduced pipe stops above the liquid pool depth of thenext pipe run. The configuration withdraws liquid from the walls of thetop pipe and introduces the fluid into the middle of the next pipe andout at 122. FIG. 9 is but one embodiment of a flow inverter system 142;other flow inverters known in the art may also be used. Typical flowinverters used in the art can be found in, for example, ChemicalEngineers' Handbook, Perry and Chilton, Ed., 6^(th) Edition, p. 5-23.Flow inverters are typically not needed in the esterification process,because the gas tends to mix the fluid. However, a flow inverter can beused in the esterification process, if needed.

[0425] The vapor disengagement system of, for example, FIG. 8 can beused without a flow inverter. In that aspect, in one embodiment, tee 139of FIG. 8 contains a weir such as shown in FIG. 9, but section 143 canbe just straight pipe and section 140 an elbow, without a flow invertertherein. Thus, in that aspect, section 142 of FIGS. 8 and 18 do notcontain the flow inverter system of FIG. 9.

[0426] Referring back to the exemplary embodiment of thepolycondensation reactor shown in FIG. 2, the polycondensation reactorpipe elevations can be continuously sloped from top to bottom. Thisconfiguration requires extreme care in calculating the angles to obtainthe desired liquid level, since strictly the liquid viscosity and pipelength (reaction along length) would control the angle for the level. Byadding weirs to each level of piping, the weirs can correct errors incalculation. Even with weirs, the liquid could overflow and continuearound a sloped horizontal spiral of the polycondensation piping.However, laminar flow would maintain the same liquid on the outside andthe same liquid on the inside of the flow path.

[0427] In the polycondensation pipe reactors of the present invention,pumps are not required between the reactor zones or sections of thepolycondensation pipe reactor. Thus, the present invention in one aspecteliminates the need for additional pumps between zones. The oligomer andpolymer in the polycondensation zones of the reactor in one aspect flowby gravity from one section to the next, and no pressure restrictingdevices are located between the reactors. Seal legs are preferably usedto maintain a pressure differential between the reactors as discussedbelow.

[0428] Referring now to FIGS. 17a and 17 b, the polycondensation reactorpreferably includes a top section 235, a middle section 236, and abottom section 237, and at least one degassing mechanism incorporatedinto the polycondensation reactor. Such a degassing mechanism is shownin one aspect in FIG. 8 and in FIG. 18 as system 133. Only one vacuumsystem is required and only one vacuum pressure is required in thepolycondensation process. However, with only one vacuum system, thevapor velocities can be extremely high and will detrimentally put liquidwith the vapor into the vacuum system. At least two, and more preferablythree levels of vacuum can be used to minimize this entrainment. Onevacuum system can ultimately supply the one or more vacuum pressuresrequired.

[0429] If only one spray system is used, this requires that the vacuumto the highest pressure zone be controlled with a control valve. Withouta spray condenser between the reactor and the control valve, this valvewill plug. When three levels of vacuum are used, with a main spraysystem for the combined two lower pressure vacuum systems and anotherspray system for the higher pressure vacuum system, then the controlvalve is after the high vacuum spray system. This valve will not plug.One vacuum train is sufficient, but two spray systems are typicallyrequired.

[0430] With reference to FIGS. 17a and 17 b, the effluent from theesterification reactor enters the polycondensation reactor at 235 andthe final product from the polycondensation process exits the system at239. The fluids traversing within the inside surface of thepolycondensation reactor also flow sequentially by the at least one (oneis the minimum, but additional degassing mechanisms reduces the vaporvelocity, hence reducing liquid entrainment into the vapor) respectivedegassing mechanism when flowing from the first to second end of thepolycondensation reactor, in which the as shown three degassingmechanisms are located respectively at the top section, the middlesection, and the bottom section of the polycondensation reactor. Thetop, middle, and bottom sections are preferably maintained at differentpressures from each other preferably by the use of seal legs.Preferably, for PET production, the pressure in the top section rangesfrom 40 to 120 millimeters mercury, the pressure in the middle sectionranges from 2 to 25 millimeters mercury, and the pressure in the bottomsection ranges from 0.1 to 5 millimeters mercury. One embodiment of theseal legs and vacuum source is disclosed in U.S. Pat. Nos. 5,466,765 and5,753,190, which are incorporated herein in their entirety. It is alsopreferred that the three degassing mechanisms are in fluid communicationwith one venting system. When the polycondensation pipe reactor is at asub-atmospheric pressure, the source of such vacuum can be any vacuumgenerating source such as, but not limited to, a vacuum pump or ejector.A preferred degassing mechanism 133 is shown in exploded view in FIG. 8.In one aspect, laminar mixing system 142 can be used and is shown inexploded view in FIG. 9. The elevational difference in the differentzones of the polycondensation reactor allows for the elimination of allpumps internal to the polycondensation reactor train. Thepolycondensation pipe reactor actually dampens inlet perturbationsdespite eliminating the use of pumps.

[0431] Alternatively, the various stages of polycondensation can bebroken up so that the effluent (bottom) from one stage is pumped to theinfluent (top) of the next stage. This allows the height of the totalsystem to be reduced because each stage is smaller in height than theoverall gravity fed system. Thus, the different vacuum sections do notneed to end up with one below the next. In one aspect, the difference inpressure that is controlled in the seal leg can be used to raise thenext section of the polycondensation reactor above the exit of thehigher pressure section. A pump can be added between polycondensationvacuum pressure zones so that all zones can start at the same elevation.This lowers the total building height for the polycondensation facility.

[0432] With reference to FIG. 18, a single zone of the polycondensationreactor is shown. That is, with reference to FIGS. 17a and 17 b, FIG. 18represents one of the zones P1, P2, or P3. Alternatively, FIG. 18 couldrepresent the entire polycondensation process. Typically, each of thezones P1, P2, and P3 is at a different pressure to maximize theefficiency in the polyester production. More or less zones can be usedfrom 1 to a plurality, for example, 2, 3, 4, 5, or more zones with 3typically be used for PET or PETG production for example. The inlet tothe zone in FIG. 18 is at 147 and the outlet at 148. Thepolycondensation fluids flow through the pipe reactor reacting from theinlet to the outlet along, in one embodiment as shown, the linear andnon-linear path. The vapor is disengaged from the polycondensationreactor with a similar piping arrangement to the esterification processat 133, as shown in FIG. 7 and as specifically shown for one embodimentof polycondensation in FIG. 8 (which were also referenced above in thediscussion of the esterification pipe reactor). FIG. 8 shows a blowup ofsection 133 of FIG. 18 where liquid and gas comes into the disengagingsystem 133. FIG. 9 shows a blow up of Section 142 of FIG. 8 and FIG. 18.FIG. 18 shows five vapor disengagement section 133. However, any numberof vapor disengagement section 133 can be used for a particular zone,from 1, 2, 3, to as many as are needed to effectively vent this system.FIG. 18 also shows an embodiment wherein the laminar mixing using a flowinverter system 142 is used, which is blown up in FIG. 9. Additionally,preferred angles for the vent system of the 90 degree angle followed bytwo 45 degree angles are shown. Other angles can also be used.

[0433] The vapor or gas in the polycondensation process shouldpreferably be disengaged from the liquid. For example, in oneembodiment, it is preferred to drive the EG byproduct from thepolycondensation reaction off as a vapor, disengage it, and remove itfrom the system. The degree of disengagement can be affected by, forexample, increasing the number of parallel pipes, which increasesdisengagement With reference to FIGS. 8 and 9, at the end of eachelevation of the polycondensation reactor 138, the liquid flows over theweir 124 inside of a tee 139 with a leg 143 directing the liquid towardthe ground to elbow 140 and then horizontally at 141. The weir (or thefluid viscosity and pipe length) in the polycondensation zones maintainsthe liquid level, L, at approximately half full in the piping. Thismaximizes the surface area. Once the fluid in the reactor is so thickthat a weir is not required to maintain level, then maintaining the pipehalf full does not maximize surface area or mass transfer rates. Thesecond leg 138 of the tee is in the direction of the flow. The third leg144 of the tee is pointed in the horizontal plane in the direction awayfrom the liquid flow. In one aspect, the vapor and entrained liquid isdisengaged by flowing through a nonlinear pipe. In one aspect, thenonlinear pipe is a pipe such that the angle from third leg 144 to thevapor exit does not proceed along a linear path. Such an angle createsan impingement plate for the entrained liquid. This impingement platecauses the entrained liquid to disengage from the vapor and return backto the liquid system. With reference to FIGS. 7, 8, and 18, variousembodiments of this entrained liquid/vapor separator are shown. After ashort horizontal run from the third tee leg, the vapor line has an elbow134, preferably a 90° elbow, directing the vapor away from the ground.The horizontal zone 144 allows the vapor to flow at a slow rate and theliquid to disengage and flow back to the main stream. After a shortvertical run 145 from the vapor elbow 134, a preferred 45° elbow 135(common pipe component with a maximum disengagement vector) is installedwith the vapor line at preferably 45° elbow 146, which is againhorizontal at 137. The angled pipe has a steep slope to provide theenergy required for the high viscosity liquid to drain back into thereactor with very low residence time. The vapor, without the liquid,passes upward into angled pipe. This horizontal pipe 137 is thencombined with the other vapor lines or is directed to the condenser orvacuum system. The vapor leaves via line 137 and the liquid goes to thenext level in line 141. The steep slope is the impingement plate for theentrained liquid. The liquid flows over the weir, and drops to the nextzone. Further polycondensation may be conducted in the next line 141.The physical layout of the pipe creates the desired functionality (flow,pressure, etc.) without any internal parts (other than a weir) orcomplicated configurations.

[0434] The ester exchange or esterification vapor piping leaving tee 36can be the same as the polycondensation piping after the 90° elbow 134directing the vapor vertically and is shown in FIG. 7g. As shown in FIG.7g, the liquid is disengaged against the angled pipe flowing back intothe liquid pool. As shown in FIG. 18, the angled pipe 136 has a steepslope to provide the energy required for the high viscosity liquid todrain back into the reactor with very low residence time. The vapor,without the liquid, passes upward into angled pipe. The gas proceeds upthe pipe and to the vapor processing equipment.

[0435] The pressure drop zone preceding the polycondensation zone has ahigh degree of mixing. The pressure let down zones between reactors alsohas high mixing and are accessible in this reactor.

[0436] Nitrogen or vapor or gas can be purged across or into the liquidof one or more polycondensation reactor sections. One potentialadvantage of this procedure is the lowering of the partial pressure ofthe diol, thereby increasing the polycondensation rate.

[0437] Referring now to FIG. 6 which is yet another embodiment of theinvention, the esterification reactor is shown dividing into a pluralityof parallel pipe reactor flow conduits 165 and 166, with the inlet beingat 164. The outlet of the parallel esterification reactors flow to thepolycondensation reactors. The polycondensation reactor is showndividing into a plurality of substantially parallel flow conduits 160,161, and 162 between the first and second ends thereof. Fluid flowingthrough the polycondensation reactor passes through one of the pluralityof flow conduits while flowing from the first end to the second end. Asshown, at least one of the flow conduits further comprises an injectionline 163 in fluid communication therewith, in which the injection lineadapted to add an additive to the monomer flowing therethrough. Thecontemplated additives may be any of those listed above.

[0438] Still referring to FIG. 6, the polycondensation reactor of thepresent invention can be used to manufacture multiple products from thesplit line. The reactor can be split at many locations to permit theincorporation of different additives, reactants or product attributes(such as inherent viscosity (IV)). For example, in FIG. 6, one monomeror oligomer is made in a single esterification section 164 (shown withtwo parallel reactors 165 and 166), and fed to two differentpolycondensation reactors 160 and 161, allowing two different melt phaseproducts to be made. The polycondensation reactions can be the same ormay differ in conditions, reactants, additives, size, or a combinationof these features or other features. As noted above, line 163 is anaddition line and the monomer is shown as being split and an additionalreactant, such as DEG, added at 163 to allow one polycondensationreactor to make a different product, such as a higher DEG product, in162. The number of splits is not limited to two; any number of splitscan be made. Similarly, the plant could be operated with some zoneemptied and not operating, allowing the plant to operate at multiplecapacities.

[0439] Returning to the design of the polycondensation pipe reactor, thepipe elevational height, pipe diameter, total length of pipe, andpressure at the inlet and outlet can vary widely depending upon theproducts made, plant capacity, and operating conditions. One of ordinaryskill in the art could readily determine these parameters using basicengineering design principles together with the disclosures herein. Thepipe elevational height is typically not critical and can be based uponthe building dimensions.

HTM Subloops

[0440] Most polyester plants have numerous HTM (Heat Transfer Media,such as oil) subloop pumps. These pumps allow temperature control ofindividual loops that is lower than the main loop header temperature.Lowering the HTM temperature reduces the wall temperatures, improves thepolymer color, lowers degradation, and allows for better temperaturecontrol.

[0441] In the present invention, allowing the header temperature to becontrolled by the hottest zone in the reactor and valves for the otherzones can eliminate these pumps. The second hottest zone is heated bythe HTM exiting the first zone. In between the two zones, a controlvalve allows flow to the Return HTM header and then a second controlvalve allows flow from the Supply HTM header. This provides theequivalent temperature control that can be obtained with Subloop pumps.Each successive zone has temperature controlled in the same manner. Allof this is made possible because the pipe reactor can be of a jacketedpipe so the pressure drop (ΔP) of the HTM across the reactor is low. Onthe other hand, for a conventional process, a CSTR relies upon coils inthe reactor and a jacketed reactor, which causes a large ΔP of the HTMacross the reactor.

[0442] Referring to FIG. 14, the flow rate in the main HTM header can bereduced and the return temperature of the HTM will be lower than theSubloop controlled system. Heat Transfer media is supplied in header 173and returned to the furnace or heat source in header 174. A differentialpressure is applied between the headers 173 and 174 to provide drivingforce for the fluid flow. The supply header 173 pressure must alsoexceed the additive pressure drop of all of the zones piped in seriesand still overcome the pressure in the return header174. Return header174 must provide adequate Net Positive Suction Head for the headerpumps. Heat Transfer Media (HTM) is supplied to Zone 172 through atemperature or flow control valve. The HTM leaving zone 172 proceeds tozone 171. If the fluid is too hot or the flow is too high, then HTM isremoved to header 174. If the fluid is too cold, fluid is added fromheader 173. If the fluid requires a higher temperature than can beobtained with the valve sizing, then fluid can be removed to header 174and replaced with fluid from header 173.

[0443] In a first embodiment, therefore, the heat transfer media controlsystem includes a first heat transfer media header through which a firstheat transfer media stream is passed; a second heat transfer mediaheader through which a second heat transfer media stream is passed; afirst heat transfer media sub-loop, through which the heat transfermedia may be passed, from the first to the second headers, respectively;and a control valve in fluid communication with a selected one of theheaders and the first sub-loop. The pressure of the first heat transfermedia stream is greater than the pressure of the second heat transfermedia stream, and the control valve is used to selectively direct atleast a portion of the first heat transfer media stream into the firstsub-loop using the pressure of the first heat transfer media stream,only, to pass the heat transfer media through the first sub-loop, and toalso control the temperature and pressure of the heat transfer mediastream being passed therethrough. An additional aspect of the systemincludes a second heat transfer media sub-loop formed separately of thefirst sub-loop and in fluid communication therewith; and a secondcontrol valve in fluid communication with the second sub-loop. Thesecond control valve selectively directs at least a portion of the firstheat transfer media stream into the second sub-loop, using the pressureof the first heat transfer media stream, to control the temperature andthe pressure of the heat transfer media being passed therethrough.

[0444] In a second embodiment, the heat transfer media control systemincludes a first heat transfer media header through which the first heattransfer media stream is passed; a second heat transfer media headerthrough which the second heat transfer media stream is passed; a firstheat transfer media sub-loop through which the heat transfer media maybe passed from the first header to the second header; a first controlvalve in fluid communication with the first header and the firstsub-loop; and a second control valve in fluid communication with thefirst sub-loop and the second header. The pressure of the first heattransfer media stream within the first header being greater than thepressure of the second heat transfer media stream within the secondheader, and one or both of the control valves is used to selectivelydirect at least a portion of the first heat transfer media stream intothe first sub-loop, using the pressure of the first heat transfer mediastream, to pass the heat transfer media through the first sub-loop, andto also control the temperature and pressure of the heat transfer mediastream being passed through the first sub-loop.

[0445] An additional aspect of the second embodiment of the inventionincludes adding a second heat transfer media sub-loop formed separatelyof the first sub-loop and in fluid communication therewith, with asecond control valve in fluid communication with the second sub-loopwherein the second control valve selectively directs at least a portionof the first heat transfer media stream into the second sub-loop, usingthe pressure of the first heat transfer media stream, to control thetemperature and the pressure of the heat transfer media being passedtherethrough. The second control valve is used to decrease thetemperature and the pressure of the heat transfer media passed thoughthe first sub-loop. An additional aspect of the invention includes athird control valve in fluid communication with the second sub-loop,wherein the third control valve selectively directs at least a portionof the first heat transfer media stream into the second sub-loop, usingthe pressure of the first heat transfer media stream, to control thetemperature and the pressure of the heat transfer media being passedtherethrough.

[0446] Still another aspect of the heat transfer media control system isthat the pressure of the heat transfer media passed through the secondsub-loop will be less than the pressure of the heat transfer mediapassed through the first sub-loop. Additionally, the second controlvalve will be used to increase the temperature and the pressure of theheat transfer media passed through the second sub-loop. Thus, in anotheraspect, the system includes a conduit extending in sealed fluidcommunication from the first sub-loop to the second sub-loop so that theheat transfer media passed though the first sub-loop is passed throughthe second sub-loop, the second control valve being in fluidcommunication with each of the first and second sub-loops, respectively,and used for controlling the temperature and pressure of the heattransfer media passed from the first sub-loop into the second sub-loop.The second control valve may also be used to lower the temperature andthe pressure of the heat transfer media passed from the first sub-loopinto the second sub-loop.

[0447] Still another aspect of the system includes a series of heattransfer media sub-loops, therefore, each subsequent sub-loop being influid communication with the immediately preceding sub-loop forreceiving the heat transfer media therefrom. This features the aspect ofthe fluid pressure of the heat transfer media passed through the seriesof heat transfer media sub-loops being lower in each subsequent sub-loopwith respect to the immediately preceding sub-loop. Also, an aspect ofthis embodiment of the system is that the temperature of the heattransfer media passed through the series of heat transfer mediasub-loops will be lower in each subsequent sub-loop with respect to theimmediately preceding sub-loop. An additional aspect is that eachrespective heat transfer media sub-loop of the series of sub-loops has afirst control valve in fluid communication with the first header and thesub-loop for increasing the temperature and pressure of the heattransfer media passed therethrough, and a second control valve in fluidcommunication with the sub-loop and the second header for decreasing thetemperature and pressure of the heat transfer media passed therethrough.

[0448] Another aspect of the heat transfer media control system is thatthe heat transfer media is passed from the first header into and throughthe first sub-loop in the absence of a heat transfer media circulatingpump, and also that the heat transfer media is passed from the firstsub-loop into the second header in the absence of a heat transfer mediacirculating pump. Similarly, it is an additional aspect of thisembodiment that the heat transfer media is passed from the first headerinto and through the first sub-loop, and passed from the first sub-loopinto the second header, respectively, in the absence of a heat transfermedia circulating pump.

[0449] The method of passing the heat transfer media through the heattransfer media system includes passing the first heat transfer mediastream through a first heat transfer media header; passing the secondheat transfer media stream through a second heat transfer media header;passing the heat transfer media from the first header through a firstheat transfer media sub-loop, in the absence of a heat transfer mediacirculating pump, with a first control valve in fluid communication withthe first header and the first sub-loop; and passing the heat transfermedia from the first sub-loop into the second header, in the absence ofa heat transfer media circulating pump, with a second control valve influid communication with the first sub-loop and the second header. Thepolycondensation fluids are moved from the first end of the pipe reactorto the second end thereof in the absence of a pump.

Minimization of Equipment

[0450] If desired, the use of liquid raw material feed tanks may beeliminated from the polyester process. As known, raw materials aredelivered to the process plant by any number of known types of deliveryvehicles, to include a pipeline, a rail car, or a tractor-trailer. Thisinvention provides that the raw materials, as delivered, may now bepumped directly to the plant from the delivery vehicle. The basis ofthis process is the NPSH curve of the pump. As known, and for examplewhen a tractor-trailer delivers the fluid(s) used, the NPSH is afunction of the fluid level within the trailer and the pressure drop ofthe fluid to the pump. The pressure drop is a function of the fluidvelocity, the fluid viscosity, and the piping configuration used. Incomparison, the head pressure from a supply tank is a function of liquidheight and density. The piping configuration of the system will beconstant in both instances. The liquid density and viscosity changesshould be small with ambient temperature changes, but if the density andviscosity changes are large they can then be obtained from a coriolismass flow meter, in known fashion.

[0451] Therefore, if the mass flow rate is known from the flow meter,then a process control computer (not illustrated) of known constructioncan take this data input, as well as any additional input data that maybe required, as discussed above, and can calculate the fluid mass withinthe trailer using the inlet pump pressure. The inlet pump pressure andflow are used to continually determine the mass of the fluid within thetrailer. During functional checkout, the pressure and flow relationshipto the fluid level within the trailer is established to correct anydeficiencies in the computer estimation.

[0452] The operating process is now described below with reference tothe fluid delivery system illustrated in FIG. 21. A first trailer 265 isparked at a pump station “P”. The trailer is connected and valved to apump 263 by opening a series of valves 251, 252, 253, 257, 261, and 276,respectively. At the same time, a second series of valves 258, 259, 272,274, and 275, are closed. The pump 263 is started and primed by goingback to the trailer 265. The system is now ready for plant operationonce the automatic valve 272 is opened. A second trailer 266 is alsoparked at the pump station, and is connected and valved to a second pump264 by opening a series of valves 254, 255, 256, 260, 262 and 273,respectively. Simultaneously, the valves 258, 259, 271, 274 and 275 areclosed. The pump 264 is started and primed by going back to the trailer266. The pump 264 system is now ready for plant operation but is left ina standby mode.

[0453] The valve 272 is opened and the plant is started. When the levelin the trailer 265 is determined to be at a certain level such as, forexample, 10% of its full level, the valve 272 is closed and the valve271 is opened simultaneously for providing a seamless supply of fluid tothe plant. Now the pump 263 is in recirculation back to the trailer 265and the pump 264 is supplying the plant from the trailer 266. The plantcontinues to run consuming fluid from trailer 266 until the leveltherein is measured to be at a certain level such as, for example, 85%of the full level. Once this occurs, the computer opens the valve 275and closes the valve 276. This pumps the remainder of the fluid contentswithin the trailer 265 into the trailer 266. The pump 263 stopsautomatically on low watts. The process control computer then closes thevalve 275.

[0454] The first trailer 265 is removed from the pump station, andanother trailer 265 full of the desired process fluid is parked at thepump station. This process is repeated with pump 263 being primed fromthe trailer 265. Then, once the fluid level within the trailer 266 ismeasured to be at a certain level such as, for example, 10% of fullvalue, the valve 271 is closed and the valve 272 is opened. The fluidlevel in the trailer 265 is used until the fluid level is measured at acertain level such as, for example, 85% of full, whereupon the remainderof the fluid within the trailer 266 is pumped into the trailer 265. Thetrailer 266 is then removed from the pump station, and another fulltrailer 266 is parked in the position of the original trailer. The pump264 is fed and primed from the new trailer 266, and the processcontinued in this fashion.

[0455] A first embodiment of the described fluid delivery systemtherefore includes at least one delivery container positioned at a pumpstation, and at least one pump in fluid communication with the at leastone delivery container, the at least one delivery container being influid communication with a valve train, the valve train being in fluidcommunication with the process plant pipe system. The fluid isselectively pumped directly from the at least one delivery containerthrough the valve train and into the process plant pipe system in theabsence of a fluid delivery feed and storage tank for otherwisereceiving and storing the fluid from the at least one delivery containertherein. Additionally, the system includes a second delivery containerpositioned at the pump station and a second pump in fluid communicationwith the second delivery container, each of the delivery containers andpumps, respectively, being in fluid communication with the valve train.The valve train is comprised of a plurality of selectively operablecontrol valves and being in fluid communication with the process plantpipe system, such that the fluid is selectively pumped directly from thefirst and second delivery containers, respectively, through the valvetrain and into the process plant pipe system in the absence of a fluiddelivery feed and storage tank.

[0456] Additional aspects of the system include a process controlcomputer, the process control computer being operably coupled to thefirst and the second pumps, respectively, and to at least one of thecontrol valves within the valve train; a mass flow meter in fluidcommunication with each of the first and the second delivery containers,respectively, and being operably coupled to the process controlcomputer; the mass flow meter being constructed and arranged to measureand transmit a fluid mass flow rate of the fluid pumped from either ofthe delivery containers to the process control computer; the processcontrol computer calculating the fluid mass within a selected one of thedelivery containers using the fluid mass flow rate and a measured inletpump pressure. Additionally, the process control computer uses the inletpump pressure and fluid flow rate flow to continually determine the massof the fluid within the selected one of the delivery containers.

[0457] The process control computer opens a first automatic controlvalve and starts the operation of the process plant; and closes thefirst automatic control valve once the fluid level within the firstdelivery container is determined by the process control computer to beat a first predetermined fluid level. An additional aspect is that asecond automatic control valve is simultaneously opened by the processcontrol computer such that the first pump recirculates the fluid fromthe first delivery container back into the first delivery container, andthe second pump supplies the fluid from the second delivery container tothe process plant. The plant is thereafter provided with the processfluid from the second delivery container until the fluid level thereinis determined by the process control computer to be at a secondpredetermined fluid level. Thereafter, the process control computeropens the first control valve and closes the second control valve suchthat the remainder of the fluid contents within the first deliverycontainer are pumped into the second delivery container. Once theprocess control computer closes the first control valve, the firstdelivery container may be replaced with a fresh delivery container inits place at the pump station. An additional aspect of the inventionincludes the process control computer reopening the second control valveand closing the first control valve such that the plant is provided withthe process fluid from the second delivery container.

[0458] The described method of this invention therefore includespositioning a first delivery container at a pump station, the firstdelivery container being in fluid communication with a first pump,positioning a second delivery container at the pump station, the seconddelivery container being in fluid communication with a second pump, andselectively pumping the fluid from each of the respective deliverycontainers directly into the valve train and into the process plant pipesystem. This method includes the aspects of operably coupling theprocess control computer to the first and the second pumps,respectively, and to at least one of the control valves within the valvetrain, and using a mass flow meter in fluid communication with each ofthe first and the second delivery containers, respectively, and beingoperably coupled to the process control computer, to measure the fluidflow passed therefrom by the first and second pumps, respectively. Theprocess control computer calculates the fluid mass within a selected oneof the delivery containers using the fluid mass flow rate and a measuredinlet pump pressure, and also uses the inlet pump pressure and the fluidflow rate flow and continually determining the mass of the fluid withinthe selected one of the delivery containers. The process controlcomputer opens a first automatic control valve and starts the operationof the process plant in response to determining the mass of the fluidwithin the selected one of the delivery containers.

[0459] Additional aspects of the method also include the process controlcomputer closing the first automatic control valve once the fluid levelwithin the first delivery container is determined by the process controlcomputer to be at a first predetermined fluid level such that the firstpump recirculates the fluid back into the first delivery container, andsimultaneously; opening a second automatic control valve such that thesecond pump supplies the fluid from the second delivery container to theprocess plant; providing the process plant with the process fluid fromthe second delivery container until the fluid level therein isdetermined by the process control computer to be at a secondpredetermined fluid level; the process control computer opening thefirst control valve and closing the second control valve such that theremainder of the fluid contents within the first delivery container arepumped into the second delivery container; the process control computerclosing the first control valve and replacing the first deliverycontainer with a fresh delivery container at the pump station; and thentransferring the remainder of the fluid from within the first deliverycontainer to the second delivery container, and thereafter continuing toprovide the process plant with the process fluid from the seconddelivery container while replacing the first fluid delivery container.

[0460] As known, in a typical polyester processing facility threedifferent distillation columns are present: A water column, a strippercolumn, and an MGM column (mixed glycol and monomer column or ethyleneglycol condensate column). Vapor from the esterification reactor is sentto the water column. There water is separated from the ethylene glycol.Low boilers (including water) are removed at the top of the column andsent to the stripper column, while ethylene glycol and other highboilers are removed at the bottom of the column and can be sent back tothe paste tank, the reactors, directed to other users, and as describedherein, back to the recycle loop.

[0461] The stripper column separates paradioxane out at the top of thestripper column which cannot be sent to the waster water treatmentfacility, and combines the paradioxane with an azeotrope of water whichis then sent to the furnace or to an oxidizer with the other low boilingpoint components. The fluids from the bottom of the stripper column aresent to the wastewater treatment facility. In one embodiment of thepresent invention, the water column is maintained by sending the lowboilers to the furnace rather than to the stripper column, and thestripper column can be eliminated. In this instance, the water column isvented to the furnace rather than sending the low boilers to thestripper column. The MGM column is also vented to the furnace.

[0462] It is also known that in a conventional polyester processingfacility, a wastewater treatment facility is required to treat theorganic waste as well as the hydraulic load (water flow) resulting fromthe process. In one aspect of the present invention, described above,the organic waste is vented to the furnace where it is burned. In aseparate aspect of the invention, and as discussed in detail herein, byeliminating many unit operations from the polyester formation processand integrating the plant, thus creating a more compact plant, a roofcan be put over the entire process plant, thus eliminating the need tosend the hydraulic load to a wastewater treatment facility because rainwater will no longer be permitted to come into contact with the processequipment, and/or any spilled process fluids. In still another aspect ofthe invention, therefore, the elimination of the organic wastes bysending these to the furnace, and the elimination of hydraulic load orwastewater by integrating the plant through the reduction of thefacility size coupled with putting a roof over the facility, eliminatesthe need for a wastewater treatment facility needed to otherwise servicethe polyester processing plant.

[0463] Environmental emissions from the plant can be reduced by ventingall of the process (i.e., the distillation columns, the scrubbers, theadsorbers, the vacuum pumps, etc,) and tank vents into a pressurizedvent header. The vent header flows to the HTM furnace and isincinerated. If all such vents are connected to this header, therefore,the unoxidized emissions from the plant will be reduced by more than 99%(typically oxidized emissions are carbon dioxide and water).Additionally, this process eliminates the need for a stripper column.

[0464] Still another feature of the present invention is that byincreasing the volume of the base portion of the respective distillationcolumns over that base volume used in conventional processes, tanks forthe products passed to and from the distillation columns can beeliminated. This reduces the amount of fluid containment area and all ofthe associated costs with any such storage tanks. Increasing the heightor diameter of the base can increase the distillation column volume. Noadditional instruments are needed on the column. In one aspect of theinvention, the base of the water column is at least 40% larger indiameter or height than a conventional water column. In this aspect, theoverall height increases by about at least 3%. In another aspect, thebase is increased at least 50% in diameter or height.

[0465] The wastewater treatment facility can be eliminated, as discussedabove, through the integration of the plant. This is particularly madepossible by eliminating environmental emissions and by eliminatingstorage tanks as previously discussed. Moreover, the plant isconstructed with a roof over all process buildings, the trailerpump/unloading station, the HTM furnace, and/or any other areas of theplant that could have the potential of COD. The wastewater from thepelletizer and the cooling tower are separated from all other wastestreams and go to the plant outfall. All rainwater, including water fromall roof areas described above, also goes to the plant outfall. A ditch,preferably double walled, is constructed between the process plant andthe HTM furnace. This preferably is a covered ditch. All remainingcontaminated wastewater goes into the ditch. All collected wastewaterwithin the ditch is pumped from the ditch to the HTM furnace where thewastewater is burned. The heat duty cost is offset by the reduction inthe cost for the capital and operating cost of a wastewater treatmentplant if all other sources of water are limited.

[0466] Also, if the plant layout is planned properly, only one conveysystem is required for the pellets or chips for a melt phase facility.The final reactor outlet is high enough so that the cutter can makepellets, which will fall by gravity into the analysis bins located belowthe cutters. In another embodiment, the analysis bins are eliminated.The pellets are conveyed to the top of the blending silo, and the bottomof the blending silo is positioned above the packaging bin. The bottomlocation and elevation of the packaging bin are high enough to allow thecontents of the packaging bin to feed by gravity into Sea bulks, trucks,or railroad cars. The packaging bin can also be eliminated by directlyfeeding the packaging equipment from the silo. The units that packagebulk bags, boxes, drums, and sacks are located under and near enough tothe packaging bin so that they can also be filled by gravity. Thereduction in convey systems reduces equipment, utility cost, andimproves product quality with the elimination of the mechanism for themelting and the stringing of the pellets.

[0467] In still another aspect of the invention, the water systems inthe plant can be minimized by combining the safety shower, the coolingtower, the cutter water, and the HTM pump coolers.

[0468] Typically, the plant safety shower system is a self containedsystem. It has a level control system fed off of the city water supply.It also has a pressurization system and a back up pressurization gas incase of a power failure. The cooling tower has a water supply used tomaintain the water level therein due to the loss of water thatevaporates, and a blowdown (purge) to keep high boiling point componentsfrom concentrating or precipitating. The cooling tower system has achemical additive system that keeps the water pH, hardness, biologicalgrowth, and the like on target. The cutter water system supplies waterto the cutter (making pellets), and make-up water is required since thewater evaporates when contacting the hot polymer strands. This systemdoes not normally have a purge, and the impurities generally leave onthe pellets, although this can cause problems. The cutter system alsohas a chemical additive system. The HTM pumps have coolers that have ahigh-pressure drop. The standard cooling tower header does not supplyenough pressure to go through the high-pressure drop coolers on the HTMpumps.

[0469] Four choices typically exist for dealing with these problems:

[0470] 1.) use supply water as once through cooling;

[0471] 2.) increase the pressure of the cooling tower water headerpaying the increased capital and pumping costs;

[0472] 3.) build a separate high pressure cooling tower header incurringthe increased capital and pumping cost; and

[0473] 4.) purchasing low pressure drop coolers for the pumps incurringthe added capital cost and voiding the warrantee.

[0474] Integrating these systems could reduce capital and operatingcosts. With the integration of the HTM systems and the elimination ofall Subloop pumps, only the main loop HTM pumps are left. The coolingwater flow required for these HTM pumps is slightly less than thecooling tower makeup water required (too much water is acceptable). Thecutter water system has higher water pressure to go to the cutters, thepressure of which is also high enough for use with the HTM pump coolers.However, after passing through the HTM pumps the water should not comeback to the cutter system since an HTM leak would contaminate theproduct. Therefore, this water from the HTM pumps should go to thecooling tower. If the cooling tower chemicals were added to the cutterwater system, it would protect the cutter water system and eliminate oneof the chemical additive systems and still supply the chemicals to thecooling tower via this purge. A purge on the cutter water system wouldnot be detrimental and could be beneficial. Pumping water from thecutter water system through the HTM pump coolers and then through thecooling tower would eliminate the additional cooling system needed forthe HTM pumps, would eliminate a chemical treatment system, and providethe needed water to all three uses. Water would still need to besupplied to the cutter water system and the safety shower.

[0475] The safety shower system needs to be purged weekly to keep thewater from being stagnant. Purging more often that this would bebeneficial, and an automatic purging would reduce cost. If the safetyshower tank is elevated then the pressurization and back uppressurization system therefor are not needed. If water entered thesafety shower tank and overflowed out the top of the tank, then the tankwould stay full and not need a level system. If the level control valvefor the cutter water system was in the line supplying the safety showertank, and the safety shower tank overflowed into the cutter water tank,then the safety shower would be continuously purged with water flowingat the make-up rate for both of the cutter water and the cooling towerwater systems. This layout would eliminate all labor and instrumentsfrom the safety shower system.

[0476] A novel integrated plant water distribution system of theinvention which addresses the aforementioned problems, and satisfies theneeds of the plant operator, is illustrated in FIG. 22. Referring now toFIG. 22, a safety shower water storage tank 290 is supplied with cleanfresh water from a suitable water source “S”, such as an off-site citywater supply (not illustrated). The safety shower tank supplies anyneeded water to the plant safety showers and eyebaths (not illustrated),and also supplies water through a first pipeline 291 to a filter andwater storage tank assembly 294 provided as a part of a separatecutter/pelletizer water tank 294. Once introduced into the waterdistribution loop, the water is passed into and through the filter andwater storage tank assembly 294. From here the filtered and cold wateris passed through the pelletizer water distribution loop by a suitablepump 295, and then passed through a downstream heat exchanger 296 tocool the water after having been passed through the pump. A filter 298is positioned in the pelletizer water distribution loop downstream ofthe pump to remove any dirt and/or small particles that may be entrainedtherein. A downstream chemical additive station 299 is provided as apart of the pelletizer water distribution loop in order to keep thewater in the pelletizer water distribution loop within controlledorganic growth, water hardness, water solubility, and corrosivityguidelines, as needed for the process being performed, as well as beingdue to the locale and water characteristics of the water supplied to thesystem. The last component of the pelletizer water distribution loop isa cutter/pelletizer station 300, the function of which is describedbelow.

[0477] Molten polymer from the plant is supplied via polymer supply line316 to a polymer extrusion die head 317 at the cutter/pelletizer station300, the die head extruding a plurality of molten polymer strands 318 inknown fashion. The molten polymer strands are cooled in thecutter/pelletizer station 300 for pelletizing and/or cutting the moltenpolymer strands with the cold, filtered water supplied through thepelletizer water distribution loop. Thereafter, the now heated and“dirty” water is passed into the filter and water storage tank assemblyto be cooled, with make up water for water lost from evaporation at thecutter/pelletizer station, which make up water is also used to purge topump 303, added from the safety shower water storage tank. The waterpassed into the filter and water storage tank assembly is then passedback through the pelletizer water distribution loop, as describedhereinabove, for re-use.

[0478] A separate water line 302 is fed from the pelletizer waterdistribution loop, and extends to a downstream pump 303 used to pass thewater to a cooling tower 304. The cooling tower is provided with a levelcontrol 306, used to maintain the level of water held in a watercollection basin 307 formed as a part of the cooling tower assembly. Thelevel control 306 has a minimum flow setting that will ensure that asatisfactory amount of water is always provided for the minimum requiredcooling flow for the pump 303. The cooling tower cools the water passedtherethrough, the water being passed from the water collection basinthrough a cooling tower water supply loop 308.

[0479] The anticipated uses of the water passed through the coolingtower water supply loop include any desired number of downstream coldwater users 311, which users may return the now “waste” water to thecooling tower water supply loop. Any water not used downstream is passedback into and through the water cooling tower, the level control valve306 drawing water from the pelletizer water distribution loop as neededto make up for lost water within the collection basin/reservoir 307.

[0480] The waste water passed back into the cooling tower water supplyloop from the downstream users is passed back into and through thecooling tower 304, and evaporates therein. The evaporation of the waterthus concentrates solids and/or contaminates within the water streampassed through the cooling tower water supply loop, so water is purgedout of the loop through a water purge line 312, as necessary, to a wateroutfall (not illustrated) with a controller 314. The pump(s) 310 supplythe force used to pass the cooled water therethrough to any and allwater users.

[0481] The water supplied to the safety shower water storage tank 290 iscontrolled by a water level control 315, which device maintains thewater level within the tank 290 at a suitable water level. Excess waterfrom the safety shower water storage tank passes therefrom through thewater line 291 and into the filter and water storage tank assembly 294of the pelletizer water distribution loop 292, where the water ishandled as described above. All water supplied to the pelletizer waterdistribution loop 292 and the cooling tower water loop 308 is suppliedfrom a suitable water supply W (potable water), as described above. Thisincludes all water added to each system for all water lost through thedownstream users 311 and the evaporation of water in thecutter/pelletizer station 300, as well as in the cooling tower 304.

[0482] Accordingly, the integrated plant water distribution system ofthis invention includes in a first embodiment a safety shower waterstorage tank in fluid communication with, and supplied by water from thewater source, a first water distribution loop in fluid communicationwith the safety shower water storage tank and being supplied with watertherefrom, a second water distribution loop in fluid communication withthe first water distribution loop, and a control valve or valves forselectively drawing water from the first water distribution loop tosupply water to the second water distribution loop. Aspects of thissystem include the safety shower water storage tank being in fluidcommunication with a separate safety shower and eye wash system; a waterpipeline extending in sealed fluid communication from the safety showerwater storage tank to the first water distribution loop, wherein thefirst water distribution loop is supplied with water from the safetyshower water storage tank as the water overflows therefrom and is passedinto the first water loop. The first water distribution loop comprises apelletizer water loop constructed and arranged to supply water to apelletizing station used to pelletize a melted plastic polymer; a filterand water storage tank; a pump constructed and arranged to pump thewater from the water storage tank through the first water distributionloop; a heat exchanger; a filter; and a chemical additive station. Theheat exchanger is positioned downstream of the pump, the filter ispositioned downstream of the heat exchanger, the chemical additivestation is positioned downstream of the filter, the pelletizing stationis positioned downstream of the chemical additive station, and thefilter and water storage tank is downstream of the pelletizing station.

[0483] Additional aspects of the integrated plant water distributionsystem include a water level control in fluid communication with thefilter and water storage tank, and a control valve intermediate and influid communication with each of the water level control and the safetyshower water storage tank. The water level control is constructed andarranged to selectively add make-up water to the filter and waterstorage tank directly from the water source. The water level control isalso constructed and arranged to selectively control the supply of waterto the safety shower water storage tank to maintain the water leveltherein at a predetermined water level.

[0484] The second water distribution loop comprises a cooling towerwater loop which includes a cooling tower, a pump constructed andarranged to pump the water from the cooling tower through the secondwater distribution loop, and at least one cooling tower water user. Thecooling tower further comprises a water collection basin formed as apart thereof for collecting the water passed therethrough. The pump ofthe cooling tower water loop is positioned downstream of the watercollection basin, and the at least one cooling tower water user ispositioned downstream of the pump and upstream of the cooling tower. Thesecond water distribution loop further comprises a purge line in fluidcommunication therewith, and a control valve in fluid communication withthe purge line for selectively passing water from the second waterdistribution loop. A second water pipeline extends in sealed fluidcommunication from the first water distribution loop to the second waterdistribution loop for providing water thereto.

[0485] One aspect of the means for selectively drawing water from thefirst water distribution loop to the second water distribution loopcomprises a second pump in fluid communication with the second waterpipeline, adapted to draw water from the first water distribution loopto the second water distribution loop therethrough. An additional aspectof the means for selectively drawing water is a water level control influid communication with the cooling tower water collection basin, and acontrol valve intermediate and in fluid communication with each of thesecond pump and the cooling tower water collection basin. The waterlevel control for the cooling tower basin is constructed and arranged toselectively add make-up water to the cooling tower water collectionbasin from the second water pipeline, and is also constructed andarranged to establish a minimum water flow setting that will ensure thata satisfactory amount of water is always provided for the minimumrequired cooling flow of the second pump.

[0486] Another aspect of this invention is thus the method ofdistributing water through an integrated plant water distributionsystem, the aspects of the method including supplying water to a safetyshower water storage tank, passing the water from the safety showerwater storage tank into the first water distribution loop, andselectively passing water from the first water distribution loop to thesecond water distribution loop. The method features the additionalaspects of selectively adding water to the first water distribution loopdirectly from the water source; passing the water in the first waterdistribution loop through the molten polymer pelletizing station;passing the water in the second water distribution loop through thewater cooling tower; selectively passing water from the second waterdistribution loop through the water purge line in sealed fluidcommunication with the second loop; and selectively passing water fromthe first water distribution loop into the cooling tower watercollection basin forming a part of the second water distribution loop.

[0487] A preferred embodiment of an integrated vacuum system for usewith the described process/process plant is illustrated in FIG. 23. Byusing the integrated vacuum system illustrated, the number of EG jetsmay be reduced, the chilled water system may be minimized, if noteliminated in some instances, and the number of components required forobtaining two stages of vacuum in the last polycondensation reactor isalso minimized.

[0488] As illustrated in FIGS. 17a and 17 b, respectively,polycondensation normally has three stages of vacuum.Here the uniquedesign of this invention integrates these last two stages of vacuum, themedium pressure and the low pressure vacuum stages. The third vacuumstage cannot be integrated because the pressure in this stage is toohigh and would not otherwise allow the EG vapor jet to have the properdifferential pressure for operation. Putting a valve in the vapor linehas led to plugging problems and is not a reliable solution.Nevertheless, two stages of vacuum can be effectively coupled.

[0489] Referring now to FIG. 23, a suitable and otherwise conventionalvacuum pump 320 pulls a vacuum on an interstage condenser 321 used tocondense components such as EG and other condensables. A first EG vaporjet 322 is installed between a spray condenser 324 and the interstage-condenser, and which vapor jet will usually have a compression ratio ofbetween 6 to 8. The liquid discharge of the interstage condenser goes toa liquid seal vessel 325, also referred to as an immersion vessel. Thedischarge from the vacuum pump, as well as the liquid discharge from thespray condenser can also be passed on to this seal vessel, or to anyother type of desired vessel. The liquid from the immersion vessel isthen pumped through a filter 326, a cooler 328, and either (a) returnedto interstage condensor 321 or spray condensor 324, or (b) is dischargedfrom this system at line 331 to, for example, the water column (notshown). Depending on the product being processed, the temperature of thesystem should be increased or decreased to control the vacuum as well asto control the buildup of low and intermediate boiling components, asknown.

[0490] The vacuum pump of the integrated vacuum system of this inventionpulls the vacuum from the polycondensation medium pressure vacuum stageor zone P2 into a top portion or region of the spray condenser through aline 244, as schematically illustrated. This medium pressurevacuum/vapor stream from the top of the final polycondensation reactoris connected to the spray condenser below the liquid cooling nozzles(not illustrated) within the top zone of the condenser. As shown, thevacuum connection extending from the spray condenser to the first EG jetis also at the top of the spray condenser, which allows thepolycondensation vapors to be condensed before going to the EG jet. Thishas the desirable effect of increasing the capability of the jet.

[0491] The polycondensation low pressure vacuum stage or zone P3 of thefinal polycondensation reactor is connected by a line 245 to a second EGjet 330, and extends from there to a bottom portion or region of thespray condenser. The vapors from this second EG jet thus enter the spraycondenser 324 at a point below the bottom liquid cooling nozzles (notillustrated) thereof. This allows the polycondensation vapors from thesecond EG jet, and the low polycondensation pressure vacuum from thebottom of the final reactor to condense without otherwise impairing ordiminishing the vacuum of the top of the polycondensation reactor.

[0492] Still referring to FIG. 23, the integrated vacuum system of theinvention also includes the necessary components for drawing a vacuumthrough the polycondensation high pressure vacuum stage or zone P1 usingthe vacuum pump 320. Accordingly, the high pressure vacuum zone is pipedinto a condenser 335 through a vacuum line 243. The vapors from the highpressure stage are cooled in the condenser 335, in known fashion. Theliquid/liquid condensate collected within the condenser is passed into asecond seal vessel 336 in fluid communication with the condenser.

[0493] This second seal vessel is in fluid communication with a pump 337which draws the liquid/liquid condensate therefrom and passes it througha downstream filter 339. Thereafter, the liquid is chilled within achiller 340 in fluid communication with the filter, and the liquidpassed back into the condenser 335 for re-use, or passed to other userswithin the plant, as desired. A vacuum line 334 extends from the top ofthe condenser 335, and is in fluid communication with the vacuum pump320 through a control valve 343.

[0494] This design therefore eliminates one EG jet train, one spraycondenser and pumping system, and only has two total EG jets rather thanthree per train. By putting all of the seal legs for the medium and lowpressure vacuum zones to the same seal vessel, the number of sealvessels has also been cut to less than half. For example a dual systemwould have five seal tanks, whereas a single system would normally havethree seal tanks. This construction thus eliminates unnecessaryequipment, instruments, and also reduces energy consumption otherwiseneeded to operate a larger vacuum system.

[0495] As described, therefore, the integrated vacuum system of theinvention includes a spray condenser in fluid communication with each ofthe medium and low pressure vacuum zones, respectively, of thepolycondensation reactor, an interstage condenser in fluid communicationwith the spray condenser; and a vacuum pump in fluid communication withthe interstage condenser. Additional aspect of the system include a sealvessel in fluid communication with each of the spray condenser, theinterstage condenser, and the vacuum pump, respectively; and a liquiddistribution system constructed and arranged to collect, filter, chill,and distribute liquid from the spray condenser and the interstagecondenser, respectively, to each of the spray condenser and theinterstage condenser, respectively. Other aspects includes the liquiddistribution system being constructed and arranged to collect liquidfrom the vacuum pump; the liquid distribution system being comprised ofa single seal vessel constructed and arranged to collect liquid fromeach of the spray condenser and the interstage condenser, respectively;and a control valve in fluid communication with the liquid distributionsystem and being constructed and arranged to selectively pass thechilled liquid to other users thereof, as desired.

[0496] Still other aspects of the system include the fluid from the lowpressure vacuum zone entering a bottom portion of the spray condenser,and the fluid from the medium pressure vacuum zone entering a spaced topportion of the spray condenser; a second spray condenser in fluidcommunication with the high pressure vacuum zone of the polycondensationreactor, the second spray condenser also being in fluid communicationwith the vacuum pump; a control valve disposed intermediate of and influid communication with each the second spray condenser and the vacuumpump; and a second liquid distribution system constructed and arrangedto collect, filter, chill, and distribute liquid passed from the secondspray condenser to at least the second spray condenser.

[0497] Yet another aspect of the integrated vacuum system of theinvention includes a spray condenser in fluid communication with each ofthe medium and low pressure vacuum zones, respectively, of thepolycondensation reactor, a first EG jet in fluid communication with thespray condenser, an interstage condenser in fluid communication with thefirst EG jet, a vacuum pump in fluid communication with the interstagecondenser, and a second EG jet in fluid communication with the lowpressure vacuum zone and the spray condenser, respectively. Additionalaspect of this embodiment of the invention include the fluid from thelow pressure vacuum zone entering a bottom portion of the spraycondenser, and the fluid from the medium pressure vacuum zone entering aspaced top portion of the spray condenser; the first EG jet extendingfrom the top portion of the spray condenser; the second EG jet being influid communication with the low pressure vacuum zone and the bottomportion of the spray condenser; and a seal vessel in fluid communicationwith the spray condenser, the interstage condenser, and the vacuum pump,respectively, the seal vessel being constructed and arranged to collectliquid and liquid condensate therein. More aspects include a pump influid communication with the seal vessel for pumping the collectedliquid therefrom; a filter in fluid communication with the pump; achiller in fluid communication with the filter and being constructed andarranged to chill the liquid passed therethrough, the chiller being influid communication with each of the spray condenser and the interstagecondenser, respectively, and wherein the liquid chilled by the chilleris passed to the spray condenser and the interstage condenser,respectively; a control valve in fluid communication with the chillerand being constructed and arranged to selectively pass chilled liquid toother users thereof, as desired; a liquid collection and chilling systemconstructed and arranged to collect, filter, and chill liquid and liquidcondensate from the spray condenser, the interstage condenser, and thevacuum pump, respectively, and to redistribute the chilled liquid to thespray condenser and the interstage condenser, respectively.

[0498] The method of collecting fluid from the final polycondensationreactor therefore includes passing the fluid from at least the mediumpressure polycondensation vacuum zone and the low pressurepolycondensation vacuum zone of the reactor into a single spraycondenser in sealed fluid communication with each of the medium and lowpressure vacuum zones, respectively, and drawing the fluid through aninterstage condenser in fluid communication with the spray condenserwith a vacuum pump in fluid communication with the interstage condenser.Additional aspect of the method include passing the fluid from the lowpressure polycondensation vacuum zone into a bottom portion of the spraycondenser, and passing the fluid of the medium pressure polycondensationvacuum zone into a spaced top portion of the spray condenser; passingthe fluid from the top portion of the spray condenser to the interstagecondenser; passing the fluid from the top portion of the spray condenserthrough a first EG jet in fluid communication with the spray condenserand the interstage condenser; passing the fluid from the low pressurepolycondensation vacuum zone through a second EG jet in fluidcommunication with the low pressure polycondensation vacuum zone and thespray condenser, respectively; collecting liquid and liquid condensatefrom the spray condenser and the interstage condenser in a seal vesselin fluid communication with each of the spray condenser and theinterstage condenser; filtering and chilling the liquid collected in theseal vessel, and passing the chilled liquid back to the spray condenserand the interstage condenser, respectively; selectively passing at leasta portion of the chilled liquid through at least one control valve influid communication therewith for use elsewhere, as desired; and passingthe fluid from the high pressure vacuum zone into a second spraycondenser in sealed fluid communication with the vacuum pump.

Absorber System

[0499] In some embodiments, it may be desirable to replace thedistillation columns with adsorbers. The adsorbers can use hot, inertgas for desorption. Inert gas is any gas, which does not react withreactants under the conditions there present. Hot gas desorptionproduces glycols with very low concentrations of water, which willimprove the ester exchange or esterification conversion. In one aspect,at least one reactant is a diol compound, and wherein at least a portionof the diol compound is removed from the process as a vapor, a liquid,or as both a vapor and a liquid, and is subjected to an adsorptionsystem to selectively recover the diol compound.

[0500] As shown in FIG. 19, the fluids from the process are fed to thefirst adsorber 182. The process fluids sent to the first adsorber 182typically comprise vapors, liquids or a mixture thereof. This processfluid normally comes from a vapor stream off of the esterificationprocess, and the liquids come from the polycondensation and otherstreams, such as pump purges, pump seals, vacuum pumps, evaporatorpurges, intercondensers, etc. The process fluid stream continues to thesecond adsorber until a component that is desired for recovery breaksthrough the bed. All previous process vapor fluids leaving the adsorberare sent to the HTM furnace for incineration via line 184. At thispoint, the bed is saturated.

[0501] The use of adsorption reduces columns, equipment, tanks,agitators, pumps, etc. and replaces them in one embodiment, with a fewsimple large pipes or tanks, a compressor, and two heat exchangers.Adsorbtion saves energy since no reflex is required like a distillationcolumn, which typically has a reflux rate equal to the product draw-offrate. Another advantage of absorption over distillation is that the diolwill be more pure, which leads to less by-product in the product, suchas lowered DEG and less coloration. Also, the by-product is reduced inthe ester exchange or esterification reactor, such as water in theesterification reactor. Water can have a significant impact on thereactor, and so, the esterificiation reactors can be smaller.

[0502] Process fluids enter adsorber bed 181 as stream 189 and exits instream 190. Stream 190 has a continuous monitoring instrument (such asan FTIR (Fourier Transform Infrared Analysis), but a single wavelengthwould be appropriate with experience, and the switching could be donewith a timer after experience, and monitoring can be accomplished withmanual grab samples) that indicates when a component to be saved isexiting the bed. Until a desired component exits, all other componentsare sent via stream 190 to stream 184. Stream 184 goes to a thermaldestruction device such as the Heat Transfer media furnace, a thermaloxidizer, a catalytic oxidizer, etc. Once bed 181 is loaded and adesired component is exiting stream 190, the process fluids are sentinto the next absorber bed.

[0503] In order to use the same drawing, bed 181 is now shown as thepartially loaded bed that is being loaded via stream 189 from thereactors. Bed 182 is the fully loaded bed described in the precedingparagraph. Bed 183 is a fully desorbed bed. Bed 181 is being loaded asdescribed in the first paragraph. Bed 182 has a hot stream of inert gas,such as nitrogen, carbon dioxide, argon, etc. supplied to it via stream191 coming from heat exchanger 188 which is heating the stream. Anyconvenient source of heat may be used such as steam, electricity, hotgas or vapor, hot liquids such as heat transfer, media, etc. Heat mayalso be exchanged between condenser streams 187, 191, 192, 193 andstream 199. Conventional air to air heat exchangers as wells as solidbed exchangers may be used. The motive force for the inert gas streamcomes from compressor or blower 186 although an eductor device may beused with inert makeup stream 197. The pressure on the inlet ofcomponent 186 is maintained by the addition of inert 197 andrecirculation stream 195.

[0504] The hot inert gas coming into bed 182 desorbs the components fromthe bed. Alternately, steam or other hot condensable vapor may be used,but this detracts from the purity of the exiting stream and alsorequires additional separation equipment for the stream. Those skilledin the art will control the flow and temperature of stream 191 toaccurately desorb bed 182 separating the desorbed components into highpurity, discrete pulses. These pulses in stream 192 are monitored by asimilar device used in stream 190. When a non-desired component isremoved from bed 182 into stream 192, a 3-way valve or multiple 2-wayvalves are switched and stream 192 is sent via stream 198 to the thermaloxidation device via stream 184. Alternately, stream 192 could passthrough a non-cooled condenser 185 and proceed to stream 184 for thermaloxidation. When a desired component is removed from bed 182 into stream192, the valves are switched and stream 192 proceeds to stream 199 andinto condenser 185. Condenser 185 can be cooled with air, refrigeratedwater, refrigerated gas, by expansive cooling, or other appropriatemeans. The cooled stream 199 will fall below the saturation temperatureand the desired component will condense from the stream as a liquid. Theliquid in stream 187 is directed to the appropriate storage containerfor that product. Once stream 192 contains a non-desired componentagain, the valves are again switched so that stream 192 goes to thethermal oxidation device. This switching process between desired andnon-desired components continues until bed 182 is totally desorbed. Bed182 then goes to standby.

[0505] Gas from condenser 185 in stream 193 will contain the desiredcomponent to be recovered, but is below the saturation temperature ofcondenser 185. So, stream 193 is sent to the fully desorbed bed 183. Bed183 adsorbs the desired components cleaning stream 193. Stream 193 exitsbed 183 as stream 194. Stream 194 is directed back to blower orcompressor 186 as stream 195. Stream 197 adds makeup inert gas tomaintain a constant inlet pressure to compressor 186.

[0506] Once bed 181 is saturated and bed 182 has been previouslydesorbed, the bed functions cycle. Bed 181 takes the place of bed 182 inthe cycle. Bed 182 takes the place of bed 183. Bed 183 takes the placeof Bed 181. During the second phase Bed 181 will be desorbed, Bed 182will catch the desired components from condenser 185. Bed 183 will besaturated with reactor vapors. Once bed 181 is desorbed and bed 183 issaturated, the next phase will begin.

[0507] Further enhancements may be necessary based on system sizes andproducts being produced. Multiple adsorber beds may be required for eachfunction as well as multiple cooler, compressors, heater, and heatexchangers. The stream 189 from the reactors may be cooled beforeentering bed 181 to improve the adsorption capacity of the bed.

Elimination of Gear Pump(s)

[0508] Most polyester plants have a gear pump between the prepolymerreactor and the finisher reactor. The pump overcomes the pressure dropbetween the two reactors since the pressure difference is not greatenough to provide the required flow. The pump is also used as a meteringdevice to provide a uniform flow to the finisher allowing stableoperation. Some processes have been constructed with the prepolymerreactor at a higher elevation than the finisher to provide the necessarypressure difference. These plants forego the uniform flow to thefinisher.

[0509] The pipe reactor system does not require a pump in thepolycondensation system since the design of the piping inherentlyprovides the pressure required to move the material to the next sectionof the plant. In addition, the pipe reactor has no level or pressurecontrol systems to provide upsets to the system that would be dampenedby the gear pump. The pipe reactor dampens inlet perturbations. Sincethe pipe system provides a uniform flow without additional dampening andprovides the head pressure necessary to provide the flow between reactorsections, it does not need a gear pump in the polycondensation section.

Combined Esterification Pipe Reactor and Polycondensation Pipe Reactor

[0510] The individual sections recited above regarding the processes andapparatuses for esterification and polycondensation apply to, and can beused in, the combination and retrofit embodiments recited below.

[0511] As shown in FIGS. 6, 17A, and 17B, the two main pipe reactorstages of the present invention can be combined into an integral unit.FIG. 17A shows one embodiment of the present invention. Theesterification reactor and polycondensation reactor are both pipereactors. Reactive material is stored and fed from tank 221. In apreferred embodiment, it is solid PTA feed directly to recirculationline 224. The reactive material proceeds to solid metering device 222from tank 221, which is on weigh cells 223. The solid PTA enters therecirculation line 224 where it is mixed with the reactive monomer fromthe esterification reactor 227, which has been recycled through line230. The mixture enters the heat exchanger 226 where it is heated. Themixture is then fed to pipe reactor 227. Part of the reaction mixture isrecycled back to line 230 to the influent of pump 225. Additional liquidadditives, such as reactants, can be fed through line 240 intopreferably the influent of pump 225. The effluent of pump 225 is fedthrough a pressure reducing device 246 to facilitate the solid feedingof the PTA from tank 221. The esterification reactor can be vented atlines 231and 232. The vapor is preferably sent to refining. FIG. 17Bdiffers from FIG. 17A, in that an additional vent line 229 is present.Vent line 229 in one aspect is located just prior to the recirculationtee as shown in FIG. 17B, to, in certain aspects, remove water from theprocess. The other portion of the reactive mixture flows through theadditional pipe reactor esterification process 228. The effluent fromthe esterification process is then optionally mixed with additionalliquid additives at 234, is fed through heat exchangers 233, and is thenfed to the polycondensation reactors 235, 236, and 237. The effluent, orcompleted polyester or polymer, is fed through gear pump 238 and exitsthe system at 239. Pressure, specifically vacuum, in PET and PETGprocesses can be controlled using vent or vacuum headers 243, 244, and245. The vent or vacuum headers 243-245 can be fed to an oxidizer, suchas an HTM furnace, an incinerator, or a thermal oxidizer. Pressuredifferential between the esterification sections or zones (E1/E2) andpolycondensation sections or zones (P1/P2/P3) can be controlled using apressure differential device, such as a seal leg 247, and the pressurebetween each of the polycondensation stages 235, 236, and 237, can becontrolled using a pressure differential device, such as a seal leg ateach of 241 and 242. In an alternative embodiment, instead of therecycle influent coming from the esterification process, the recycleinfluent can come from the polycondensation process, for example, as aslip stream off of effluent 239 (not shown in figure). This can increasethe liquid polymer uniformity.

[0512] One skilled in the art will also appreciate that the reactors ofthe present invention can be used to construct new plants, as well as toenhance or improve existing plants or to increase capacity. The pipereactors can be used to replace or can be inserted within a section ormultiple sections of an existing plant that is causing a technical orcapacity limitation. In one aspect, an esterification, polycondensation,or both pipe reactor apparatus(es) is constructed and arranged to beplaced in fluid communication with a conventional reactor for making apolyester monomer or polymer. For example, FIG. 5 shows possibleconfigurations where the second esterification reactor 212 does not haveenough volume to feed the polycondensation reactor 213 at its fullcapacity. In this situation, a pipe reactor 214 may be added between thefirst and second esterification reactors (211 and 212 respectively). Ifadditional residence time is required in the first polycondensationreactor 213, the pipe reactor 215 can be installed above the top of thefirst polycondensation reactor. Similarly, jacketed pipe can be added toincrease disengagement surface area to reduce liquid entrainment. Vaporremoved from the system is withdrawn via lines 216 and 217. Additionalpipe could be added to increase the heat transfer area. These pipingmodifications can be installed with the plant running (the pipe can evenbe routed to an outside wall to have enough room for the installation)except for the two end tie-ins. Then during a short shutdown, thetie-ins can be made, effectively adding capacity or performanceenhancement. These pipe reactor retrofits can be in series or inparallel to the existing facility CSTR or other type conventionalreactor(s). When the pipe reactor retrofit is in parallel to theconventional reactor, each of the respective pipe reactor andconventional reactor can be selectively operated, such that either onlyone of the reactors is operating at one time, or both of the reactorscan be operated simultaneously.

[0513] Alternatively, the pipe reactor retrofit can replace the existingreactor(s). In one embodiment, there is provided a polyester productionsystem, comprising the pipe reactor of the present invention retrofittedto a conventional polyester process comprising a conventional polyesterreactor, wherein the conventional reactor has been disabled from theproduction system. In another aspect, there is provided a method ofretrofitting a pipe reactor to a conventional polyester processcomprising (a) retrofitting the pipe reactor of the present invention ina conventional polyester process comprising a conventional polyesterreactor; and (b) disabling the conventional reactor from the process. Asused herein, disabling with respect to the conventional process refersto preventing the fluid from flowing to the conventional process, by,for example, providing a valve upstream of the inlet and downstream ofthe outlet to the conventional reactor and valving the conventionalprocess off or disconnecting the inlet and outlet of the conventionalreactor from the process system.

[0514] In the processes and apparatuses described herein, there can begreater than one esterification stage or zone and/or greater than onepolycondensation stage or zone. These multiple reactors can be placed inseries or in parallel.

[0515] Previous sections described the parameters for designing the pipereactor systems of the present invention. For large plants, it may notbe possible to acquire large enough pipe diameter to construct thereactor and meet the parameters. For such plants, a plurality of pipereactors can be operated in parallel. Multiple parallel pipe reactorscan be installed and combined at various locations within or between thezones. To minimize cost, the initial starting section of the reactor canbe mixed before splitting. This will eliminate the purchase ofadditional feed systems. The vapor lines can all go to the same vacuumtrain. The polycondensation reactors can share the same vacuum andcondenser systems. Thus, the only additional equipment, and costincurred, is the additional piping required.

[0516] In another embodiment, one single pipe reactor produces thepolyester polymer from initial pre-monomer reactants. In this pipereactor, reactants to make the monomer are fed in at one end andpolyester polymer product is output at the other end. This is especiallyapplicable for polyester processes that do not have separateesterification and polycondensation steps. In this embodiment, the aboveaspects with respect to the separate esterification and polycondensationreactors and processes are applicable to this single pipe reactorprocess, such as the use of a weir, vapor removal and liquiddisengagement, geometrical orientation of the pipe reactor, etc.

[0517] Accordingly, in one aspect, the pipe reactor divides into aplurality of substantially parallel flow conduits extending between theinlet and the outlet thereof, and wherein the reactant flowing throughthe pipe reactor passes through one of the plurality of flow conduitswhile flowing through the reactor. In another aspect, at least twoseparate esterification pipe reactors are provided, each of whichproduces the same or a different polyester monomer, and wherein thefluid polyester monomer exiting the respective esterification pipereactors is directed into the first end of the polycondensation pipereactor. In another aspect, at least two separate polycondensation pipereactors are provided, each of which produces the same or a differentpolyester polymer, and wherein each fluid polyester monomer exiting therespective esterification pipe reactors is directed to the first end ofat least one of the respective polycondensation pipe reactors. Inanother aspect, the esterification pipe reactor comprises a plurality ofesterification reactors positioned in parallel to one another with acommon inlet. In another aspect, the polycondensation pipe reactorcomprises a plurality of polycondensation reactors positioned inparallel to one another with a common first end. In this embodiment, aco-reactant can be added to at least one of the plurality ofpolycondensation reactors but not to all of the polycondensationreactors to thereby produce at least two different polyester products.

Some Expected Advantages of the Present Invention

[0518] One benefit of the present invention is that the design allowsthe reactor to be constructed in areas that contain interferences. Thepipe can be fabricated around columns, beams, other pipes, otherreactors, distillation columns, etc.

[0519] Also, many embodiments of the present invention do not requirepressure or level control. The pressure at the bottom of theesterification or ester exchange reactor is controlled by the pressurelosses due to friction, the static head from the reactor liquidcontents, and the back pressure on the vapor lines leaving the reactor.Since the goal is to reduce the pressure in the reactor in a prescribedpressure profile, the reactor piping is configured to produce theprofile. This eliminates the need for pressure control with valves. Butit is possible to control the distillation or vapor exhaust pressure andadd this delta pressure to the entire esterification or ester exchangereactor.

[0520] Nearly every aspect of the conventional polymerization train isgreatly simplified by the pipe reactor of the present invention. Theinstrumentation, valves and control loops required are greatly reduced,and pumps, reactor agitators, reactor screws, and associated sealsystems are eliminated. Except for a pump, if one is used for arecirculation group, the pipe reactor systems of the present inventionhave little or even no moving parts. The reduction and removal of thesecomponents from the plant greatly reduces the amount of computer andcontrol equipment required, capital costs, maintenance costs and utilityconsumption. The pipe reactor can be welded without gaskets, whichreduces emissions out of the reactor and air leakage into the reactor,thereby improving product quality. The substantial reductions inequipment and control systems also provide decreased operating costs.

[0521] The pipe reactors of the present invention can be constructed andinstalled in less time than reactor vessels. The piping can be shop orfield prefabricated. The pipe reactor sizes can be designed to allow thereactor sections to be shipped by standard trucks, shipping containers,lorries, etc. without obtaining costly and slow oversize or overweightshipping permits. The prefabrication allows modular plant designs wherethe piping can be constructed, pressure tested, and insulated in theshop, reducing field construction time and at a lower cost.

[0522] The liquid volume required for polyester pipe reactor design ofthe invention is substantially less than a conventional polyesterprocess. Additionally, the amount of particular by-products produced canbe greatly reduced by utilizing a pipe reactor design of the instantinvention. In one aspect of the instant invention, wherein PET isproduced, the instant invention can achieve a level of DEG impurity inthe final produce of less than 1.2 weight percent, in another aspectless than or equal to 1.0 weight percent, in another aspect 0.74-1.0weight percent. This is to be contrasted with a typical conventionalprocess for making PET, wherein the typical range for DEG impurity levelis from 1.2 weight percent to 2.0 weight percent. In fact, this reducedamount of DEG impurity in the final product can be achievedsimultaneously with a drastic liquid volume reduction achievable withthe polyester pipe reactor design of the instant invention.

EXAMPLES

[0523] The following examples are put forth-so as to provide those ofordinary skill in the art with a complete disclosure and description ofhow the compounds, compositions, articles, devices and/or methodsclaimed herein are made and evaluated, and are intended to be purelyexemplary of the invention and are not intended to limit the scope ofwhat the inventors regard as their invention. Efforts have been made toensure accuracy with respect to numbers (e.g., amounts, temperature,etc.), but some errors and deviations should be accounted for. Unlessindicated otherwise, parts are parts by weight, temperature is in ° C.or is at ambient temperature, and pressure is at or near atmospheric.

[0524] ASPEN modeling was used for the data below. Where ASPEN modelingis referenced in the examples, it is ASPEN 10.2, service patch 1, withPolymers Plus, and ASPEN's PET Technology, except as indicated below.The esterification reactor is modeled as a series of 5 CSTR reactormodels followed by a plug flow model.

Example 1

[0525] Using ASPEN modeling, exemplary pipe lengths and heat exchangeareas werecalculated for a pipe reactor system for each of PET andPETG.The results are shown in Table 1 below. TABLE 1 EsterificationPolycondensation Pipe Diameter in  14 12  14  16 PET Plant Pipe ft 7331775 1905 Length Stage 1 Stage 2 PET Plant Heat ft² 2200  2000 ExchangerArea PETG Plant Pipe ft  79 75  255  680 Length Stage 1 Stage 2 Stage 3PETG Plant Heat ft² 2200  1900 Exchanger Area

Example 2

[0526] The liquid volume required for a polyester pipe reactor design issubstantially less than a conventional polyester process. For example,ASPEN modeling was run to compare to a 300 million pounds per year PETbottle plant. The results are set forth in Table 2 below. TABLE 2Esterification Standard Plant 100 m³ Pipe Reactor 8.4 m³ % Reduction 92%Polycondensation Standard Plant 35.6 m³ Pipe Reactor 14.2 m³ % Reduction60% Total Plant Standard 135.6 m³ Pipe Reactor 22.6 m³ % Reduction 83%

Examples 3-7

[0527] Various ASPEN modeling was run to determine operating conditionsand performance results for various polyesters of the invention. Themodeling was based upon an apparatus of the invention of either FIG. 17aor 17 b as noted in the Tables below. The inherent viscosity (I.V.) ismeasured by dissolving of 0.25 g of polymer in 50 mL in the solvent,which consists of 60% phenol and 40% 1,1,2,2-tetracholorethane byweight. The measurement is made at 25 deg C. using either a ViscotekDifferential or Modified Differential Viscometer using ASTM D 5225,“Standard Test Method for Making Solution Viscosity of Polymers with aDifferent Viscometer.” The results for Examples 3-7 are set forth belowin Tables 3-7,respectively. TABLE 3 HOMO PET - Bottle Polymer RecycleRate 5 parts monomer to 1 part PTA by weight Production Rate 300 millionpounds/year EG to PTA feed mole 1.6 ratio Polycondensation zonePolycondensation zone Polycondensation zone Reactor (See FIG. 17A)Esterification 1 2 3 Temperature (C.) 296 296 296 296 Pressure (psig) 10down to 2 Pressure (torr abs) 61 10 0.5 Liquid volume (m3) 16.2 3.7 3.39.9 E1 P1 P2 P3 12 in pipe (ft) 632 253 14 in pipe (ft) 935 830 16 inpipe (ft) 1875 heat exchanger (ft2) 2200 2200 Finished Product IV 0.60dL/g DEG 0.78 wt % Acid Ends 33 mole equivalent per 1 million gramsVinyl Ends 1.5 mole equivalent per 1 million grams

[0528] TABLE 4 PETG Copolyester (20.5 wt. % CHDM) Recycle Rate 10 partsmonomer to 1 part PTA by weight Production Rate 95 million pounds/yearEG to PTA Feed mole 3.5 ratio Polycondensation zone Polycondensationzone Polycondensation zone Reactor (See FIG. 17A) Esterification 1 2 3Temperature (C.) 255 255 275 275 Pressure (psig) 47 down to 25 Pressure(torr abs) 120 5 0.5 Liquid volume (m3) 4.6 4.0 5.0 3.2 E1 P1 P2 P3 12in pipe (ft) 213 85 14 in pipe (ft) 201 254 16 in pipe (ft) 680 heatexchanger (ft2) 2000 2000 Finished Product IV 0.75 dL/g

[0529] TABLE 5 HOMO PET - Bottle Polymer Recycle Rate 5 parts monomer to1 part PTA by weight Production Rate 300 million pounds/year EG to PTAfeed mole 1.6 ratio Polycondensation zone Polycondensation zonePolycondensation zone Reactor (See FIG. 17B) Esterification 1 2 3Temperature (C.) 296 296 296 296 Pressure (psig) 10 down to 2 Pressure(torr abs) 11 10 0.5 Liquid volume (m3) 84 1.7 2.7 9.8 E1 E2 P1 P2 P3 12in pipe (ft) 318 127 14 in pipe (ft) 630 1005 16 in pipe (ft) 1875 heatexchanger (ft2) 2000 2000 Finished Product IV 0.60 dL/g DEG 0.94 wt %Acid Ends 35 mole equialent per 1 million grams Vinyl Ends 1.5 moleequivalent per 1 million grams

[0530] TABLE 6 HOMO PET - Fiber Polymer Recycle Rate 5 parts monomer to1 part PTA by weight Production Rate 300 million pounds/year EG to PTAfeed mole 1.6 ratio Polycondensation zone Polycondensation zonePolycondensation zone Reactor (See FIG. 17B) Esterification 1 2 3Temperature (C.) 296 296 296 296 Pressure (psig) 10 down to 2 Pressure(torr abs) 11 10 0.5 Liquid volume (m3) 8.4 1.9 2.4 7.7 E1 E2 P1 P2 P312 in pipe (ft) 313 125 14 in pipe (ft) 704 893 16 in pipe (ft) 1473heat exchanger (ft2) 2000 2000 Finished Product IV 0.55 dL/g DEG 0.94 wt%

[0531] TABLE 7 PETG Copolyester (20.5 wt % CHDM) Recycle Rate 10 partsmonomer to 1 part PTA by weight Production Rate 95 million pounds/yearEG to PTA feed mole 3.5 ratio Polycondensation zone Polycondensationzone Polycondensation zone Reactor (See FIG. 17B) Esterification Zone 1Zone 2 Zone 3 Temperature (C.) 255 255 275 275 Pressure (psig) 47 downto 25 Pressure (torr abs) 120 5 0.5 Liquid volume (m3) 2.3 2.5 5.0 3.2E1 E2 P1 P2 P3 12 in pipe (ft) 106 43 14 in pipe (ft) 125 254 16 in pipe(ft) 680 heat exchanger (ft2) 2000 2000 IV 0.75 dL/g

[0532] In comparing Table 3 to Table 5, the following can be observed.With no vapor disengagement in the verification process (Table 3 data),the DEG by-product is 0.78 weight percent, versus Table 5 data, whichdoes have the vapor disengagement in the esterification section of thereaction and produces a DEG by-product of 0.94 weight percent. However,with the vapor disengagement in esterification system, the liquid volumeis reduced from 16.2 m³ down to 8.4 m³ (compare Table 5 with Table 3).Removing water during the esterification process, as shown in Table 5,drives the reaction to produce monomer but also drives the reaction toproduce additional DEG. However, the liquid volume of the reactor isdrastically reduced. In this case, for PET, the volume reductionsupercedes the increased rate of DEG production and provides a finalproduct with slightly higher DEG but with the liquid volume of thereactor reduced by almost 50%. This would be expected to result in asubstantial capital investment savings and operating expense savings forPET production.

[0533] Additionally, both Tables 3 and 5 show that the DEG by-product of0.78 weight percent and 0.94 weight percent respectively, are lower thanthat typically found using a conventional CSTR process, which is from1.2 to 2.0 weight percent.

[0534] Additionally, as noted in Tables 3-6, the reactors are run hotterthan conventional CSTR reactors. In the embodiment shown in Tables 3-6,the reactors were run at 296° C., as contrasted to conventional CSTRreactors, which are typically run at about 262° C. Surprisingly, thepipe reactors able to be run hotter than a CSTR without the negativeside effects of increased DEG production, as shown in the final productdata in Tables 3-6. It may be theorized that this is due to the smallerresidence time in the pipe reactor as compared to a CSTR reactor. Thehotter reaction temperature also enhances the process by allowing theincreased vaporization of water off of and out of the process.

Example 8 Lab-Model Comparison

[0535] Lab Scale Reactor

[0536] A lab scale esterification pipe reactor was built to demonstratesuch esterification of PTA and EG in a laboratory setting. The lab unitconsisted of a pipe reactor made of 664.75 inches of 0.5″ 18 BWGstainless tubing heated by electric tracing, a 1200 ml receiver withagitator for receiving the output of the pipe reactor and acting as adisengagement zone to allow the removal of vapors, a recirculatingmonomer gear pump which pumps liquid oligomer from the receiver backinto the inlet of the pipe reactor, and a PTA/EG paste feed system whichfeed raw materials into the recirculating loop.The reactor was startedby charging a PTA based CHDM modified (2.5 weight percent) oligomer ofapproximately 96% conversion into the receiver (C-01) and filling thepipe reactor with this oligomer in recirculating mode. Afterrecirculating the oligomer at temperature, a PTA/EG paste feed wasintroduced into the recirculating flow. After the reactor reached steadystate, samples were taken from the C-01 receiver at a rate equal to theproduct generation rate.

[0537] These samples were analyzed for percent conversion by proton NMRanalysis to determine the extent of reaction that took place in the pipereactor. Percent conversion based on Esters was determined by Proton NMRusing a Trifluoroacetic Anhydride Method:

[0538] Ten mg of the sample to be analyzed is dissolved in 1 ml of asolvent mixture of chloroform-d with 0.05% Tetramethylsilane(TMS)/trifluoroacetic acid-d/trifluoroacetic anhydride in a 72/22/8volume ratio. The mixture is heated to 500 C and stirred as needed tocompletely dissolve the sample to be analyzed.

[0539] The appropriate amount of the sample solution is transferred intoa 5 mm NMR tube and the tube is capped. The proton NMR signal isrecorded using an average of 64 signals collections. The NMR signalusing a 600 MHz NMR and a NMR pulse sequence is collected which givesquantitative proton NMR signals and also decouples the carbon 13 NMRfrequencies. The NMR spectrum is analyzed by measuring the correct areasand calculating the percent conversion of acid groups to ester groups bythe areas and calculations below:

[0540] Areas between the following chemical shift points referenced toTMS are measured, and percent conversion calculated using the formula.

[0541] Area A=7.92 ppm to 8.47 ppm

[0542] Area B=5.01 ppm to a valley between 4.82 and 4.77 ppm

[0543] Area C=4.82 ppm to a valley between 4.74 and 4.69 ppm

[0544] Area D=A valley between 4.28 ppm and 4.18 ppm to a valley between4.10 and 4.16 ppm

[0545] Area E=A valley between 4.10 ppm and 4.16 ppm to a valley between4.0 and 4.08 ppm

[0546] Area F=8.6 ppm to 8.9 ppm

[0547] Area G=7.55 ppm to 7.8 ppm

[0548] Percent Conversion=100*(B+(0.5*C)+D+(0.5*E))/(A+F+G)

[0549] The samples were also analyzed by gas chromatograph for percentDEG by mass to determine the rate of the side reaction. The effect ofresidence time and recirculation ratio was seen by varying the feed rateof the paste Results from laboratory runs can be seen in Table 8 below.TABLE 8 Recirc Paste Feed Feed Temp Pressure Rate Rate Mole RatioMeasured Measured Experiment (° C.) (psig) (lbs/hr) (lbs/hr) (EG/PTA) %Conversion weight % DEG 1 285 0 67 1 1.8 94.2% 1.1% 2 285 0 67 1 1.893.7% 1.1% 3 285 0 67 1 1.8 92.5% 1.4% 4 285 0 67 1.5 1.8 92.7% 1.0% 5285 0 67 2 1.8 90.9% 0.6% 6 285 0 67 2.5 1.8 87.2% 0.7% 7 285 0 67 3 1.864.2% 0.2% 8 285 0 67 3.5 1.8 67.1% 0.6% 9 285 0 67 4 1.8 51.9% 0.3% 10 285 0 67 3.5 1.8 77.4% 0.3%

[0550] Model Comparison

[0551] An ASPEN model was used to simulate the lab apparatus previouslydescribed in this example. In this case, ASPEN 11.1 with Polymers Plus,and ASPEN's PET Technology was used for the modeling with a modelconfiguration similar to the one described for examples 1-7. Neithermodel configuration nor software were significantly different from thatused in Examples 1-7. In order to correctly simulate the dissolution ofPTA into the oligomer at different conditions in the lab, it wassometimes necessary to add dissolution kinetics to the model. Table 9shows three comparisons of lab runs with the model without dissolutionkinetics included; this model was found to be of reasonable accuracywhen the experimental conditions resulted in completely dissolved PTA asin these runs. Table 9 also shows two examples of comparisons of labruns with the model including the dissolution kinetics; this modelincluding the dissolution kinetics closely matches the measuredconversion when free PTA is present at the end of the lab scale pipereactor as in these runs. Conversion is defined in this context as thepercentage of reactive (acid if use PTA as here) end groups in theliquid phase that are esterified as measured at the outlet of reactor.TABLE 9 Completely Dissolved PTA - No Dissolution Kinetics in ModelPaste Monomer Paste Weight % Model feed Circulation Temp. Mole RatioUnreacted Predicted Measured (g/min) (g/min) (° C.) (EG/PTA) PTA (%Conversion) (% Conversion) 8 507 263.2 1.8 0.00 97.053 95.170 8 507253.9 1.8 0.00 96.645 93.750 15  507 265.5 1.8 0.00 96.269 91.630

[0552] PTA Not Completely Dissolved/Dissolution Kinetics in Model PasteMonomer Paste Weight % Model feed Circulation Temp Mole Ratio Unreactedpredicted Measured (g/min) (g/min) (° C.) (EG/PTA) PTA (% Conversion) (%Conversion) 19 507 261.5 1.8 2.93 90.935 86.500 15 507 261.5 1.8 3.3490.228 85.490

[0553] Throughout this application, various publications are referenced.The disclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the state of the art to which this invention pertains.

[0554] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope or spirit of the invention. Otherembodiments of the invention will be apparent to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A process for making a polyester polymer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface, the esterification pipe reactor comprising a substantially empty pipe; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a polycondensation pipe reactor formed separately of the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface, the polycondensation pipe reactor comprising a substantially empty pipe; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 2. The process of claim 1, wherein the reactants comprise terephthalic acid or dimethylterephthal ate.
 3. The process of claim 2, wherein the polyester polymer is PET or PETG.
 4. A process for making a polyester polymer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid, wherein the reactants comprise terephthalic acid or dimethylterephthalate; (c) providing a polycondensation pipe reactor formed separately of the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 5. The process of claim 4, wherein the polyester polymer is PET or PETG.
 6. A process for making a polyester polymer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a polycondensation pipe reactor formed separately of the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 7. The process of claim 6, wherein the reactants do not comprise an anhydride.
 8. The process of claim 6, further comprising at least one weir attached to the interior surface of the esterification pipe reactor and wherein the esterification fluids flow over the weir.
 9. The process of claim 6, wherein the polycondensation pipe reactor further comprises at least one weir attached to the inside surface thereof and wherein the polycondensation fluids flow over the weir.
 10. The process of claim 9, further comprising at least one polycondensation fluid flowing through a flow inverter, wherein the flow inverter is proximate to and downstream of the weir.
 11. The process of claim 6, further comprising recirculating a portion of the process fluids and directing the recirculation effluent back to and therethrough the esterification reactor.
 12. The process of claim 6, further comprising removing vapors from the esterification pipe reactor intermediate its inlet and its outlet and/or proximate its outlet through a vent comprising substantially empty pipe.
 13. The process of claim 6, further comprising removing vapors from the polycondensation pipe reactor intermediate its inlet and its outlet and/or proximate its inlet or outlet through a vent comprising substantially empty pipe.
 14. The process of claim 12 or 13, wherein the vent further comprises an upstanding degas stand pipe coupled to the vent, wherein the degas stand pipe has a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the inlet end; and wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at a complimentary angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 15. The process of claim 14, wherein the first section is oriented at about from a 10 to about an 80 degree angle relative to the first section, and the third section is oriented at from about an 80 to about a 10 degree angle relative to the second section.
 16. The process of claim 14, wherein the first section is oriented at about a 45 degree angle relative to the first section, and the third section is oriented at about a 45 degree angle relative to the second section.
 17. The process of claim 6, wherein the esterification pipe reactor inlet is positioned at least 20 vertical feet below the esterification pipe reactor outlet.
 18. The process of claim 17, wherein the inlet is positioned at least 50 vertical feet below the outlet.
 19. The process of claim 17, wherein the inlet is positioned at least 100 vertical feet below the outlet.
 20. The process of claim 17, wherein the inlet is positioned from 50 to 200 vertical feet below the outlet.
 21. The process of claim 17, wherein the inlet is positioned from 90 to 150 vertical feet below the outlet.
 22. The process of claim 6, wherein the esterification pipe reactor is disposed in a substantially vertical orientation, such that the inlet is disposed vertically below the outlet, and the reactants and polyester monomer flow in an upward direction within the pipe reactor.
 23. The process of claim 6, wherein the esterification pipe reactor is disposed in a substantially horizontal orientation.
 24. The process of claim 6, wherein the polycondensation pipe reactor is substantially horizontally oriented.
 25. The process of claim 6, wherein the fluids present in the esterification pipe reactor are in a bubble or froth flow regime.
 26. The process of claim 6, wherein the fluids present in the polycondensation pipe reactor are in a stratified flow regime.
 27. The process of claim 6, wherein the esterification pipe reactor and polycondensation pipe reactor each have alternating linear and non-linear sections extending in their respective lengthwise direction between the respective inlets and outlets thereof.
 28. The process of claim 6, further comprising a seal leg positioned between and in fluid communication with the esterification process and the polycondensation process for controlling the pressure between the esterification and polycondensation processes.
 29. The process of claim 6, wherein the polycondensation reactor includes at least two different sections in fluid communication with one another, each section being of a different fluid pressure, and wherein a seal leg is positioned between and in fluid communication with each such section for controlling the pressure between the respective reactor sections.
 30. The process of claim 6, wherein the polycondensation reactor includes a top section, a middle section, and a bottom section, and wherein the pressure is reduced in the polycondensation reactor, the reducing step comprising at least three degassing mechanisms incorporated into the polycondensation reactor so that the polycondensation fluids traversing within its inside surface also flow sequentially by the three respective degassing mechanisms when flowing from the first end to the second end of the polycondensation reactor, and wherein the three degassing mechanisms are located respectively at the top section, the middle section, and the bottom section of the polycondensation reactor.
 31. The process of claim 30, wherein the top, the middle, and the bottom sections of the polycondensation reactor are maintained at different pressures from each other.
 32. The process of claim 7, wherein the esterification pipe reactor and the polycondensation pipe reactor both comprise substantially empty pipe.
 33. A process for making a polyester polymer from a plurality of reactants, comprising: (a) providing a combined esterification and prepolymer polycondensation pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester oligomer within the pipe reactor and the polyester oligomer exits from the outlet thereof, wherein the reactants and the polyester oligomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a polycondensation pipe reactor formed separately of the combined esterification prepolymer pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification/prepolymer pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester oligomer into the first end of the polycondensation pipe reactor so that the oligomer flows through the polycondensation reactor, the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the oligomer and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 34. A process for making a polyester polymer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a polycondensation pipe reactor integrally combined with the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 35. A process for making a polyester oligomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a prepolymer polycondensation pipe reactor formed separately of the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form the oligomer within the polycondensation pipe reactor, and the oligomer exits from the second end of the reactor, wherein the monomer and the oligomer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 36. A process for making a polyester oligomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor and react with each other to form a polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; (c) providing a prepolymer polycondensation pipe reactor integrally combined with the esterification pipe reactor, the polycondensation pipe reactor in fluid communication with the esterification pipe reactor, the polycondensation pipe reactor having a first end, a second end, and an inside surface; and (d) directing the fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form the oligomer within the polycondensation pipe reactor, and the oligomer exits from the second end of the reactor, wherein the monomer and the oligomer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 37. The process of claim 8, wherein the at least one weir is disposed proximal to the outlet of the esterification pipe reactor.
 38. The process of claim 37, wherein the weir has a body portion circumscribed by an edge, a portion of the edge being a connecting edge and a remaining portion of the edge being a top edge, the connecting edge being of a size to be complementarily received by a portion of the inside surface of the esterification reactor and attached thereto, wherein the weir acts as a barrier for the esterification fluids so that the esterification fluids flow over the top edge of the weir when flowing from the inlet to the outlet of the esterification reactor.
 39. The process of claim 38, wherein the body portion of the weir has at least two opposed sides, the weir further defining at least one opening in one of said sides and extending therethrough such that the esterification fluids flow through the at least one opening as well as over the top edge of the weir when flowing through the weir.
 40. The process of claim 8, wherein a section of the body portion of the weir is detachably removed in order to allow the esterification fluids to pass therethrough instead of over the top edge of the weir.
 41. The process of claim 37, wherein the interior surface of the esterification reactor has an inner diameter, the esterification reactor further comprising a reducer located immediately downstream of the weir, the reducer having a diameter less than the inner diameter of the esterification reactor upstream and downstream of the reducer.
 42. The process of claim 41, wherein the reducer has a lower end with an aperture defined therein and through which the esterification fluids flow when traversing from the upstream section of the reactor to the downstream section thereof, the lower end of the reducer being spaced from the inside surface of the downstream section.
 43. The process of claim 42, wherein the lower end of the reducer is spaced from a top surface of the esterification fluids flowing through the downstream section of the reactor.
 44. The process of claim 9, wherein the weir has a body portion circumscribed by an edge, a portion of the edge being a connecting edge and a remaining portion of the edge being a top edge, the connecting edge being of a size to be complementarily received by a portion of the inside surface of the polycondensation reactor and attached thereto, wherein the weir acts as a barrier for the polycondensation fluids so that the polycondensation fluids flow over the top edge of the weir when flowing from the first end to the second end of the polycondensation reactor.
 45. The process of claim 44, wherein the body portion of the weir has opposed sides, the opposed sides defining at least one opening therebetween, and wherein the polycondensation fluids flow through the opening as well as over the top edge of the weir.
 46. The process of claim 9, wherein a section of the body portion of the weir is detachably removable to allow the polycondensation fluids to pass therethrough instead of over the top edge of the weir.
 47. The process of claim 6 or 9, wherein the polycondensation reactor is formed as a plurality of contiguous interconnected sections in which the polycondensation fluids flow through the inside surface of each section traversing from the first end to the second end of the polycondensation reactor.
 48. The process of claim 47, wherein each section of the polycondensation reactor forms an angle with a vertically-oriented plane, the angle being greater than zero degrees.
 49. The process of claim 47, wherein the polycondensation reactor further comprises at least one weir attached to the inside surface thereof, the at least one weir being located adjacent a juncture of each of the interconnected reactor sections.
 50. The process of claim 49, wherein the weir has a body portion circumscribed by an edge, a portion of the edge being a connecting edge and a remaining portion of the edge being a top edge, the connecting edge being of a size to be complementarily received by a portion of the inside surface of the polycondensation reactor and attached thereto, wherein the weir acts as a barrier so that the polycondensation fluids flow over the top edge of the weir.
 51. The process of claim 50, wherein the body portion of the weir has opposed sides, the opposed sides defining at least one opening therebetween, wherein the polycondensation fluids flow through the opening as well as over the top edge of the weir.
 52. The process of claim 49, wherein the inside surface of the polycondensation reactor has an inner diameter, the polycondensation reactor further comprising a reducer located immediately downstream of each respective weir, the reducer having a diameter smaller than the inner diameter of the adjacent polycondensation reactor sections upstream and downstream of the reducer.
 53. The process of claim 52, wherein the reducer forms a part of the juncture of each pair of interconnected reactor sections formed by an upstream section and a downstream section, the reducer being connected to the upstream section and extending into the downstream section.
 54. The process of claim 53, wherein the reducer has a lower end having an aperture through which the polycondensation fluids flow when traversing from the upstream section to the downstream section of the reactor, the lower end of the reducer being spaced from the inside surface of the downstream section.
 55. The process of claim 54, wherein the lower end of the reducer is spaced from a top surface of the polycondensation fluids flowing through the downstream section.
 56. The process of claim 6, wherein the esterification fluids are not recirculated.
 57. The process of claim 11, wherein the effluent from the recirculation is directed to the esterification reactor proximate the inlet of the esterification reactor.
 58. The process of claim 11, wherein the effluent from the recirculation is directed to the esterification reactor adjacent the inlet of the esterification reactor.
 59. The process of claim 11, wherein the effluent from the recirculation is directed to the esterification reactor between the inlet and the outlet of the esterification reactor.
 60. The process of claim 11, wherein the effluent from the recirculation is directed to the esterification reactor upstream of the inlet of the esterification reactor.
 61. The process of claim 11, wherein the influent to the recirculation is in fluid communication with the esterification reactor between the inlet and outlet thereof.
 62. The process of claim 11, wherein the influent to the recirculation is in fluid communication with the esterification reactor proximate the outlet thereof.
 63. The process of claim 11, wherein the influent to the recirculation is in fluid communication with the polycondensation reactor.
 64. The process of claim 11, wherein the influent to the recirculation is in fluid communication with the polycondensation reactor proximate the outlet thereof.
 65. The process of claim 11, wherein the recirculating step is performed using a recirculation loop having an influent and an effluent, the effluent being in fluid communication with the pipe reactor proximal the inlet, wherein the fluids flowing through the recirculation loop are each recirculation fluids.
 66. The process of claim 65, wherein the influent being in fluid communication with the pipe reactor between the inlet and outlet thereof or proximal the outlet thereof.
 67. The process of claim 65, wherein the recirculation loop further comprises a recirculation pump located intermediate the influent and the effluent thereof for increasing the pressure of the recirculation fluids flowing therethrough.
 68. The process of claim 67, further comprising decreasing the pressure of the recirculation fluids at a location downstream of the recirculation pump.
 69. The process of claim 68, wherein the pressure decreasing step is performed using a pressure decreasing device of an eductor, a siphon, an exhauster, a venturi nozzle, a jet or an injector through which at least a portion of the recirculation fluids flow.
 70. The process of claim 68, wherein the pressure decreasing step is performed using an eductor.
 71. The process of claim 69, further comprising feeding at least one type of solid reactant into the recirculation loop which is dissolved by the recirculation fluids before flowing to the effluent of the recirculation loop.
 72. The process of claim 71, wherein the feeding step is performed using a feeding conduit having a discharge end in fluid communication with the recirculation loop adjacent or at the pressure decreasing device, wherein the reactant is drawn into the recirculation loop from the decreased pressure of the recirculation fluids developed by the pressure decreasing device.
 73. The process of claim 72, wherein the pressure decreasing device comprises an eductor.
 74. The process of claim 72, wherein the recirculating step and the feeding step collectively perform the step of adding at least one type of a reactant into the pipe reactor proximal the inlet.
 75. The process of claim 72, including a feeding conduit having a receiving end opposed to a discharge end, and wherein the feeding step further comprises: (a) a reactant storage device for storing the reactant to be fed into the recirculation loop; (b) a solid metering device for receiving the reactant from the solid reactant storage device; and (c) a loss in weight feeder in communication with the solid metering device and also in communication with the receiving end of the feeding conduit, wherein the reactant is fed into the recirculation loop from the solid reactant storage device, to the solid metering device, into the loss in weight feeder, and then through the feeding conduit to be drawn into the recirculation line adjacent the pressure decreasing device.
 76. The process of claim 71, wherein the reactant fed into the recirculation loop is terephthalic acid.
 77. The process of claim 76, further comprising injecting a second reactant, which is a fluid, into the recirculation loop upstream of the pressure decreasing device.
 78. The process of claim 76, further comprising injecting a second reactant, which is a fluid, into the recirculation loop downstream of the pressure decreasing device.
 79. The process of claim 76, further comprising injecting a second reactant, which is a fluid, into the recirculation loop through a recirculation pump seal.
 80. The process of claim 77, wherein the recirculating step, the feeding step, and the injecting step collectively perform the step of adding at least two types of reactants into the pipe reactor proximal the inlet thereof.
 81. The process of claim 77, 78 or 79, wherein the second reactant is ethylene glycol.
 82. The process of claim 68, further comprising removing vapors from the recirculation loop proximal to its influent and upstream of the pump, between the pump and the pressure decreasing device, or downstream of the pressure decreasing device.
 83. The process of claim 82, wherein the removing step comprises a vent incorporated into the recirculation loop so that the recirculation fluids flow through the vent when flowing from the influent to the effluent of the recirculation loop.
 84. The process of claim 83, wherein the vent reduces the flow rate of the recirculation fluids to create a stratified flow regime.
 85. The process of claim 83, wherein the vent comprises a flat-on-bottom reducer.
 86. The process of claim 83, wherein the vent is substantially horizontally disposed so that the recirculation fluids flowing therethrough are flowing substantially horizontally.
 87. The process of claim 86, wherein the vent further comprises an upstanding degas stand pipe coupled to the vent, wherein the degas stand pipe has a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the receiving end.
 88. The process of claim 87, wherein the degas stand pipe is non-linear extending in its lengthwise direction between its receiving end and its venting end, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the venting mechanism, a second section coupled to the first section and oriented at about a forty-five degree angle relative to the first section in plan view, and a third section coupled to the second section and oriented at about a forty-five degree angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 89. The process of claim 87, wherein the venting end of the degas stand pipe is in fluid communication with ambient so that the pressure of the venting end is at substantially atmospheric pressure.
 90. The process of claim 87, wherein the degas stand pipe further comprises a flow control device within the degas stand pipe for controlling the flow of fluids therethrough.
 91. The process of claim 90, wherein the flow control device comprises an orifice.
 92. The process of claim 83, wherein the recirculation loop further comprises a plurality of elbows, a first elbow disposed upstream of the venting mechanism and a second elbow disposed downstream of the venting mechanism.
 93. The process of claim 65, further comprising feeding at least one type of reactant from a paste tank into the recirculation loop.
 94. The process of claim 12 or 13, wherein the vent reduces the flow rate of the fluids flowing therethrough to create a stratified flow regime.
 95. The process of claim 12 or 13, wherein the vent comprises a flat-on-bottom reducer.
 96. The process of claim 12 or 13, wherein the vent is substantially horizontally disposed so that the fluids flowing therethrough are flowing substantially horizontally.
 97. The process of claim 12 or 13, wherein the vent further comprises an upstanding degas stand pipe coupled to the vent, wherein the degas stand pipe has a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the inlet end.
 98. The process of claim 97, wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at about a forty-five degree angle relative to the first section in plan view, and a third section coupled to the second section and oriented at about a forty-five degree angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 99. The process of claim 97, wherein the venting end of the degas stand pipe is in fluid communication with ambient so that the pressure of the venting end is at substantially atmospheric pressure.
 100. The process of claim 97, wherein the degas stand pipe further comprises a flow control device within the degas stand pipe for controlling the flow of fluids therethrough.
 101. The process of claim 100, wherein the flow control device comprises an orifice.
 102. The process of claim 97, wherein the pipe reactor further comprises a plurality of elbows, a first elbow disposed upstream of the vent and a second elbow disposed downstream of the vent.
 103. The process of claim 97, wherein the venting end of the degas stand pipe is in fluid communication with a vacuum source so that a sub-atmospheric pressure exists in the standpipe and at the inside surface of the polycondensation reactor.
 104. The process of claim 97, wherein the polycondensation reactor includes a top section, a middle section, and a bottom section, and wherein the reducing step comprises at least three degassing mechanisms incorporated into the polycondensation reactor so that the polycondensation fluids traversing within its inside surface also flow sequentially by the three respective degassing mechanisms when flowing from the first end to the second end of the reactor, and wherein the three degassing mechanisms are located respectively at the top section, the middle section, and the bottom section of the reactor.
 105. The process of claim 104, wherein the top, the middle, and the bottom sections of the reactor are maintained at different pressures from each other.
 106. The process of claim 105, wherein the pressure in the top section is in the range of from 40 to 120 millimeters mercury, the pressure in the middle section is in the range of from 2 to 25 millimeters mercury, and the pressure in the bottom section is in the range of from 0.1 to 5 millimeters mercury.
 107. The process of claim 104, wherein the three degassing mechanisms are in fluid communication with a single vacuum source and a single condenser system.
 108. The process of claim 97, wherein the degas stand pipe is non-linear extending in its lengthwise direction between its receiving end and its venting end.
 109. The process of claim 108, wherein the degas stand pipe is formed of at least two contiguous sections, each such section being in fluid communication with the other, and wherein the outlet of each such section is positioned horizontally with or disposed vertically above the inlet of each respective section.
 110. The process of claim 109, wherein the contiguous section adjacent the venting end is oriented substantially horizontally.
 111. The process of claim 6, further comprising heating the fluids flowing through the pipe reactor.
 112. The process of claim 111, wherein the pipe reactor has an exterior surface, and wherein the heating step comprises placing a heat transfer media in thermal communication with a portion of the exterior surface of the pipe reactor along at least a lengthwise portion of the pipe reactor between the inlet or first end and the outlet or second end thereof of the esterification and/or the polycondensation reactor, respectively.
 113. The process of claim 112, wherein the heat transfer media comprise a plurality of electrical heating components wrapped about the exterior surface of the pipe reactor.
 114. The process of claim 111, wherein the pipe reactor has an exterior surface, and wherein the heating step comprises: (a) a jacket pipe circumscribing the exterior surface of the pipe reactor along a portion of the length thereof between the inlet and outlet, the jacket pipe having an inner surface larger than the exterior surface of the pipe reactor for forming an annular space therebetween; and (b) supplying heat transfer media within the annular space formed between the exterior surface of the pipe reactor and the inner surface of the jacket pipe.
 115. The process of claim 114, wherein the heat transfer media comprises a liquid, a vapor, a steam, electrical heating components, or a combination thereof.
 116. The process of claim 115, wherein the heat transfer media comprises a combination of liquid and steam that flows within the annular space in a direction counter to the direction of the reactant flowing through the pipe reactor.
 117. The process of claim 113, wherein the heating step comprises passing the reactants and the monomers through a heat exchanger located in the pipe reactor within a recirculation loop positioned at an intermediate point between the respective ends of the esterification reactor.
 118. The process of claim 111, wherein the heating step comprises passing the reactants and the monomers through a heat exchanger disposed proximate and in fluid communication with the outlet of the esterification pipe reactor.
 119. The process of claim 118, wherein the heat exchanger is in fluid communication with and is proximate to or within a seal leg.
 120. The process of claim 111, wherein the heating step comprises passing the polycondensation fluids through a heat exchanger positioned intermediate the first end and the second end of the polycondensation pipe reactor.
 121. The process of claim 6, wherein at least one of the reactants is added in a heated state or as a hot vapor.
 122. The process of claim 116, wherein the heat transfer media is moved through the annular space in the absence of a subloop pump.
 123. The process of claim 6, further comprising introducing an additive into the esterification or polycondensation pipe reactor.
 124. The process of claim 123, wherein the additive comprises a catalyst, a coreactant, or a mixture thereof.
 125. The process of claim 123, wherein the additive comprises DEG, CHDM, or a combination of both.
 126. The process of claim 123, wherein the pipe reactor has an exterior surface and further comprises: (a) a sealable channel extending through the pipe reactor allowing fluid communication between its exterior surface and the interior surface of the pipe reactor; and (b) an injector for injecting the additive into the reactant flowing within the pipe reactor.
 127. The process of claim 126, wherein the injector comprises a pump.
 128. The process of claim 126, wherein the pipe reactor further comprises at least one elbow, seal leg, or heat exchanger, and wherein the sealable channel traverses through a portion of the elbow or seal leg, or proximate to and upstream of the heat exchanger.
 129. The process of claim 123, wherein the additive is added by a gravity flow thereof passing into the pipe reactor.
 130. The process of claim 6, wherein the pressure of the reactant fluids at the interior surface of the pipe reactor adjacent the inlet is greater than the pressure of the reactant fluids at the interior surface of the reactor adjacent the outlet.
 131. The process of claim 130, wherein the adding step is preformed by a pump that discharges the reactants at a pressure substantially the same as the pressure at the interior surface of the reactor, adjacent the inlet thereof.
 132. The process of claim 130, wherein the pressure of the fluids flowing through the pipe reactor continually decreases as the fluids move from the inlet toward the outlet thereof.
 133. The process of claim 6, wherein the fluids flowing through the pipe reactor pass through a plurality of adjacent stages of increasing and decreasing fluid pressure zones, respectively, as the fluids move from the inlet toward the outlet of the reactor.
 134. The process of claim 6, wherein the esterification pipe reactor is substantially linear extending in its lengthwise direction between the inlet and the outlet thereof.
 135. The process of claim 6, wherein the esterification or polycondensation pipe reactor is non-linear extending in its lengthwise direction between the inlet and the outlet thereof.
 136. The process of claim 135, wherein the pipe reactor is serpentine in front plan view.
 137. The process of claim 135, wherein the pipe reactor further comprises a plurality of elbows, each elbow changing the direction of the fluid flow within the pipe reactor relative to a stationary horizontal plane.
 138. The process of claim 135, wherein the pipe reactor is constructed is arranged to obtain a predetermined pressure profile, in which the pressure of the reactant is substantially constant along a portion of the pipe reactor extending horizontally, and the pressure of the reactant decreases at an increasing rate along a portion of the inner surface of the pipe reactor as that portion of the pipe reactor extends in a more vertical orientation.
 139. The process of claim 6, wherein a first stage of the polycondensation pipe reactor having an inlet and an outlet, is positioned wherein the inlet to the polycondensation pipe reactor is adjacent, vertically above, and in fluid communication with the outlet of the esterification pipe reactor.
 140. The process of claim 6, wherein gravity moves the polycondensation fluids from the first end toward the second end of the reactor.
 141. The process of claim 6, wherein the polycondensation reactor is divided into a plurality of substantially parallel flow conduits extending between the first end and the second end thereof, and wherein fluid flowing through the polycondensation reactor passes through one of the plurality of flow conduits while flowing therethrough.
 142. The process of claim 6, wherein the polycondensation reactor is substantially linear extending in its lengthwise direction between its first end and its second end.
 143. The process of claim 6, wherein the polycondensation pipe reactor is disposed in a substantially vertical orientation.
 144. The process of claim 28, wherein the seal leg has a heat exchanger disposed proximate to the seal leg or within the seal leg for heating the esterification fluid.
 145. The process of claim 29, wherein at least one seal leg has a heat exchanger disposed proximate to the seal leg or within the seal leg for heating the polycondensation fluid.
 146. The process of claim 6, wherein the polycondensation reactor has at least two sections of a first section and a second section, and wherein the pressure is reduced in the polycondensation reactor, the reducing step comprising at least two degassing mechanisms incorporated into the polycondensation reactor so that the polycondensation fluids traversing within its inside surface also flow sequentially by the two respective degassing mechanisms when flowing from the first end to the second end of the polycondensation reactor, and wherein the two degassing mechanisms are located respectively at the first section and the second section of the polycondensation reactor.
 147. The process of claim 6, wherein the first and second sections of the polycondensation reactor are maintained at different pressures from each other.
 148. The process of claim 6, wherein the reactants comprise terephthalic acid and ethylene glycol.
 149. The process of claim 6, wherein the reactants comprise dimethyl terephthalate and ethylene glycol.
 150. The process of claim 6, wherein the reactants comprise terephthalate acid, ethylene glycol and CHDM.
 151. The process of claim 6, wherein the polyester is PET, PETG, poly(cyclohexane)-dimethylene terephthalate, polyester formed from CHDM and dimethyl cyclohexanedicarboxylate, a liquid crystalline polyester, or a biodegradable polyester.
 152. The process of claim 6, wherein the polyester is PET.
 153. The process of claim 6, wherein the polyester is PETG.
 154. The process of claim 6, wherein the polyester is not polycarbonate or PBT, or a reactant of phthalic anhydride or maleic anhydride.
 155. The process of claim 6, wherein at least two reactants are added into the pipe reactor proximal the inlet thereof.
 156. The process of claim 148, wherein in the adding step, the terephthalic acid is pumped from a paste mix tank into the pipe reactor proximal the inlet thereof.
 157. The process of claim 6, wherein the pipe reactor divides into a plurality of substantially parallel flow conduits extending between the inlet and the outlet thereof, and wherein the reactant flowing through the pipe reactor passes through one of the plurality of flow conduits while flowing through the reactor.
 158. The process of claim 6, wherein at least two separate esterification pipe reactors are provided, each of which produces the same or a different polyester monomer, and wherein the fluid polyester monomer exiting the respective esterification pipe reactors is directed into the first end of the polycondensation pipe reactor.
 159. The process of claim 158, wherein at least two separate polycondendsation pipe reactors are provided, each of which produces the same or a different polyester polymer, and wherein each fluid polyester monomer exiting the respective esterification pipe reactors is directed to the first end of at least one of the respective polycondensation pipe reactors.
 160. The process of claim 6, wherein at least two separate polycondensation pipe reactors are provided, each of which produces the same or a different polyester polymer, and wherein the fluid polyester monomer exiting the esterification pipe reactor is directed into the respective first ends of each of the polycondensation pipe reactors.
 161. The process of claim 6, wherein the esterification pipe reactor comprises a plurality of esterification reactors positioned in parallel to one another with a common inlet.
 162. The process of claim 6, wherein the polycondensation pipe reactor comprises a plurality of polycondensation reactors positioned in parallel to one another with a common first end.
 163. The process of claim 162, wherein a co-reactant is added to at least one of the plurality of polycondensation reactors but not to all of the polycondensation reactors to thereby produce at least two different polyester products.
 164. The process of claim 6, wherein the interior surface and inside surface is substantially circular in cross section.
 165. The process of claim 6, wherein the esterification or polycondensation pipe reactor interior surface is formed of a catalytic material.
 166. The process of claim 6, wherein at least one reactant is a diol compound, and wherein at least a portion of the diol compound is removed from the process as a vapor, a liquid, or as both a vapor and a liquid, and is subjected to an adsorption system to selectively recover the diol compound.
 167. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, an interior surface, and at least one weir attached to the interior surface thereof; and (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid, and wherein the esterification fluids flow over the weir.
 168. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, and wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; and (c) recirculating a portion of the process fluids and directing the recirculation effluent back to and therethrough the esterification reactor proximate the inlet of the esterification reactor or between the inlet and outlet of the esterification reactor.
 169. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid; and (c) removing vapors from the pipe reactor intermediate its inlet and its outlet and/or proximate its outlet through a vent of empty pipe.
 170. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface, the inlet being positioned at least 20 vertical feet below the outlet; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, and wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid.
 171. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid, and wherein the fluids present in the pipe reactor are in a bubble or froth flow regime.
 172. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface, wherein the pipe reactor has alternating linear and non-linear sections extending in its lengthwise direction between the inlet and outlet thereof; (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the reactants and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid.
 173. A process for making a polyester monomer from a plurality of reactants, comprising: (a) providing an esterification pipe reactor having an inlet, an outlet, and an interior surface; and (b) adding at least one reactant into the pipe reactor proximal the inlet so that the reactants flow through the pipe reactor, the reactants reacting with each other to form the polyester monomer within the pipe reactor and the polyester monomer exits from the outlet thereof, wherein the at least one reactant and the polyester monomer flowing through the esterification pipe reactor are each an esterification fluid.
 174. The process of one of claims 167-173, wherein the pipe reactor comprises substantially empty pipe.
 175. The process of claim 173, further comprising a seal leg positioned between and in fluid communication with the esterification process and a polycondensation process for controlling the pressure between the esterification and polycondensation processes.
 176. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, and an inside surface, the first end being disposed vertically above the second end, the polycondensation pipe reactor having alternating linear and non-linear sections extending in its lengthwise direction between its first end and its second end; and (b) directing a fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 177. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, an inside surface, and at least one weir attached to the inside surface thereof, wherein the pipe reactor is made of a substantially empty pipe; and (b) directing a fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid, and wherein at least one of the polycondensation fluids flows over the weir.
 178. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, and an inside surface; and (b) directing a fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid; and (c) removing vapors from the pipe reactor intermediate its inlet and its outlet and/or proximate its inlet or outlet through a vent comprising substantially empty pipe.
 179. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, and an inside surface; and (b) directing a fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacting to form an oligomer and then the oligomer reacting to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid, and wherein the fluids present in the pipe reactor are in a stratified flow regime.
 180. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, and an inside surface; and (b) directing a fluid polyester monomer into the first end of the polycondensation pipe reactor so that the monomer flows through the polycondensation reactor, the monomer reacts to form an oligomer and then the oligomer reacts to form the polymer within the polycondensation pipe reactor, and the polymer exits from the second end of the reactor, wherein the monomer, the oligomer, and the polymer flowing through the polycondensation pipe reactor are each a polycondensation fluid.
 181. The process of one of claims 176, 178, 179, or 180, wherein the pipe reactor comprises a substantially empty pipe.
 182. The process of one of claims 176, 177, or 178, wherein the fluids present within the pipe reactor are in a stratified flow regime.
 183. The process of one of claims 177-179, wherein the polycondensation pipe reactor has alternating linear and non-linear sections extending in its lengthwise direction between its first end and its second end.
 184. The process of claim 180, wherein the polycondensation pipe reactor is substantially horizontally oriented.
 185. The process of claim 180, wherein the polycondensation reactor includes at least two different sections in fluid communication with one another, each section being of a different fluid pressure, and wherein a seal leg is positioned between and in fluid communication with each such section for controlling the pressure between the respective reactor sections.
 186. The process of claim 180, wherein the polycondensation reactor includes a top section, a middle section, and a bottom section, and wherein the vapor is reduced in the polycondensation reactor, the reducing step comprising at least three degassing mechanisms incorporated into the polycondensation reactor so that the polycondensation fluids traversing within its inside surface also flow sequentially by the three respective degassing mechanisms when flowing from the first end to the second end of the polycondensation reactor, and wherein the three degassing mechanisms are located respectively at the top section, the middle section, and the bottom section of the polycondensation reactor.
 187. The process of claim 186, wherein the top, the middle, and the bottom sections of the polycondensation reactor are maintained at different pressures from each other.
 188. A process for making a polyester polymer, comprising: (a) providing a polycondensation pipe reactor having a first end, a second end, and an inside surface; and (b) directing a fluid polyester oligomer into the first end of the polycondensation pipe reactor so that the oligomer flows through the polycondensation pipe reactor, the oligomer reacting to form the polyester polymer within the polycondensation pipe reactor and the polyester polymer exits from the second end thereof.
 189. An apparatus for producing a polyester oligomer or polymer, comprising: (a) an esterification pipe reactor having an inlet, an outlet, and an interior surface through which esterification fluid reactants are passed; and (b) a polycondensation pipe reactor formed separately of and in fluid communication with the esterification reactor, wherein the polycondensation reactor has an inlet, an outlet, and an interior surface through which at least one polycondensation fluid reactant is passed, wherein the esterification and polycondensation reactors comprise substantially empty pipe.
 190. An apparatus for producing a polyester oligomer or polymer, comprising: (a) an esterification pipe reactor having an inlet, an outlet, and an interior surface through which esterification fluid reactants are passed; and (b) a polycondensation pipe reactor formed separately of and in fluid communication with the esterification reactor, wherein the polycondensation reactor has an inlet, an outlet, and an interior surface through which at least one polycondensation fluid reactant is passed.
 191. The apparatus of claim 190, further comprising a recirculation loop having an influent and an effluent, the effluent being in fluid communication with the esterification pipe reactor.
 192. The apparatus of claim 190, further comprising at least one weir attached to the interior surface of the esterification pipe reactor and wherein the esterification fluids flow over the weir.
 193. The apparatus of claim 190, further comprising at least one weir attached to the interior surface of the polycondensation pipe reactor and wherein the polycondensation fluids flow over the weir.
 194. The apparatus of claim 190, further comprising a vent in fluid communication with the esterification reactor, the vent further comprising an upstanding degas stand pipe coupled to the vent, the degas stand pipe having a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the receiving end, and wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at a complimentary angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 195. The apparatus of claim 190, further comprising a vent in fluid communication with the polycondensation reactor, the vent further comprising an upstanding degas stand pipe coupled to the vent, the degas stand pipe having a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the receiving end, and wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at a complimentary angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 196. The apparatus of claim 190, wherein the esterification pipe reactor inlet is positioned at least 20 vertical feet below the esterification pipe reactor outlet.
 197. The apparatus of claim 190, wherein the polycondensation pipe reactor is substantially horizontally oriented.
 198. The apparatus of claim 190, wherein the esterification pipe reactor and polycondensation pipe reactor each have alternating linear and non-linear sections extending in their respective lengthwise direction between the respective inlets and outlets thereof.
 199. The apparatus of claim 190, further comprising a seal leg positioned between and in fluid communication with the esterification reactor and the polycondensation reactor for controlling the pressure between the esterification and polycondensation reactors.
 200. The apparatus of claim 190, wherein the polycondensation reactor includes at least two different sections in fluid communication with one another, each section being of a different fluid pressure, and wherein a seal leg is positioned between and in fluid communication with each such section for controlling the pressure between the respective reactor sections.
 201. The apparatus of claim 190, wherein the polycondensation reactor includes a top section, a middle section, and a bottom section, and further comprising at least three degassing mechanisms incorporated into the polycondensation reactor so that the polycondensation fluids traversing within its inside surface also flow sequentially by the three respective degassing mechanisms when flowing from the first end to the second end of the polycondensation reactor, and wherein the three degassing mechanisms are located and are in fluid communication with respectively the top section, the middle section, and the bottom section of the polycondensation reactor.
 202. The apparatus of one of claims 191-201, wherein the esterification pipe reactor and the polycondensation pipe reactor both comprise substantially empty pipe.
 203. An esterification pipe reactor apparatus for producing a polyester monomer, comprising: (a) an esterification pipe reactor having an inlet, an outlet, and an interior surface; and (b) a recirculation loop having an influent and an effluent, the effluent being in fluid communication with the esterification pipe reactor.
 204. The apparatus of one of claims 191 or 203, wherein the effluent is in fluid communication with the reactor adjacent the inlet thereof.
 205. The apparatus of one of claims 191 or 203, wherein the effluent is in fluid communication with the reactor between the inlet and outlet thereof.
 206. The apparatus of one of claims 191 or 203, wherein the influent is in fluid communication with the reactor between the inlet and outlet thereof.
 207. The apparatus of one of claims 191 or 203, wherein the influent is in fluid communication with the reactor proximate the outlet thereof.
 208. The apparatus of one of claims 191 or 203, wherein the influent is in fluid communication with a second reactor, wherein the second reactor is downstream of the esterification reactor.
 209. An apparatus for producing a polyester monomer, oligomer, or polymer, comprising: (a) a pipe reactor having an inlet, an outlet, and an interior surface through which the fluid reactants are passed; and (b) a weir connected to a portion of the interior surface of the pipe reactor and adjacent the outlet thereof, wherein the reactor comprises substantially empty pipe.
 210. An apparatus for producing a polyester monomer, oligomer, or polymer, comprising: (a) a pipe reactor having an inlet, an outlet, and an interior surface through which the fluid reactants are passed; and (b) a vent in fluid communication with the reactor, the vent further comprising an upstanding degas stand pipe coupled to the vent, the degas stand pipe having a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the receiving end, and wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at a complimentary angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 211. The apparatus of claim 210, wherein the vent is substantially horizontally disposed so that the fluids flowing therethrough are flowing substantially horizontally.
 212. The apparatus of claim 210, wherein the first section is oriented at from about a 10 to about an 80 degree angle relative to the first section, and the third section is oriented at from about an 80 to about a 10 degree angle relative to the second section.
 213. The apparatus of claim 210, wherein the first section is oriented at about a 45 degree angle relative to the first section and the third section is oriented at about a 45 degree angle relative to the second section.
 214. An apparatus for producing a polyester monomer, oligomer, or polymer comprising: (a) a pipe reactor having an inlet, an outlet, and an interior surface through which the fluid reactants are passed.
 215. The apparatus of one of claims 203 or 210, wherein the reactor comprises substantially empty pipe.
 216. The apparatus of claim 214, wherein the pipe reactor inlet is positioned at least 20 vertical feet below the pipe reactor outlet.
 217. The apparatus of claim of 214, wherein the pipe reactor is substantially horizontally oriented.
 218. The apparatus of claim 214, wherein the pipe reactor has alternating linear and non-linear sections extending in their respective lengthwise directions between the inlet and outlet thereof.
 219. The apparatus of claim 214, wherein the reactor comprises substantially empty pipe.
 220. The apparatus of claim 214, further comprising a seal leg in fluid communication with and proximate the outlet of the reactor.
 221. The apparatus of claim 214, wherein the reactor includes at least two different sections in fluid communication with one another, each section being of a different fluid pressure, and wherein a seal leg is positioned between and in fluid communication with each such section for controlling the pressure between the respective reactor sections.
 222. The apparatus of claim 214, wherein the reactor includes a top section, a middle section, and a bottom section, and further comprising at least three degassing mechanisms incorporated into the reactor so that the fluids traversing within its inside surface also flow sequentially by the three respective degassing mechanisms when flowing from the first end to the second end of the reactor, and wherein the three degassing mechanisms are located and are in fluid communication with respectively the top section, the middle section, and the bottom section of the reactor.
 223. The apparatus of claim 190, further comprising a conventional reactor for making a polyester monomer or polymer, wherein the esterification or polycondensation pipe reactor apparatus is constructed and arranged to be placed in fluid communication with the conventional reactor.
 224. The apparatus of claim 223, wherein the conventional reactor is a CSTR or reactive distillation, stripper, or rectification column.
 225. The apparatus of claim 223, wherein the pipe reactor is connected in series with the conventional reactor.
 226. The apparatus of claim 223, wherein the pipe reactor is connected in parallel to the conventional reactor.
 227. The apparatus of claim 190, further comprising: (a) a plurality of vent lines, each said vent line having a first end and a spaced second end, and a vent header having a first end and a spaced second end, the first end of each respective vent line being connected to the vent discharge of each process, and the second end of each respective vent line being connected to the first end of the vent header; and (b) the second end of the vent header being connected to an oxidizer.
 228. The apparatus of claim 227, wherein the oxidizer is an HTM furnace, an incinerator, or a thermal oxidizer.
 229. The apparatus of claim 227, wherein the vent header is under vacuum.
 230. The apparatus of claim 190, further comprising a continuous roof over each polyester polymer process building, truck unloading and pump station, and oxidizer, thereby eliminating the need for a wastewater treatment facility.
 231. The apparatus of claim 190, further comprising a column constructed and arranged to condense the vapor from the process, the column having a base, the volume of the base being sufficiently large enough to eliminate the need for column feed and product tanks.
 232. The apparatus of claim 231, wherein the column is a water column, MGM column, or stripper column.
 233. A polyester production system, comprising the pipe reactor apparatus of claim 190, retrofitted to a conventional polyester process comprising a conventional polyester reactor, wherein the conventional reactor has been disabled from the production system.
 234. A method of retrofitting a pipe reactor to a conventional polyester process comprising: (a) retrofitting the pipe reactor apparatus of claim 190 in a conventional polyester process comprising a conventional polyester reactor; and (b) disabling the conventional reactor from the process.
 235. An apparatus for venting a process of gas or vapor while effectively disengaging liquid from the gas or vapor, the liquid, gas and vapor being fluids, separating the liquid from the gas or vapor, and returning the liquid back to the process, comprising: (a) a vessel or process pipe containing (i) liquid and (ii) gas or vapor; and (b) a vent in fluid communication with the vessel or process pipe, the vent further comprising an upstanding degas stand pipe coupled to the vent, the degas stand pipe having a receiving end in fluid communication with the vent and an opposed venting end disposed vertically above the receiving end, and wherein the degas stand pipe is non-linear extending in its lengthwise direction between the receiving end and the venting end thereof, and wherein the degas stand pipe is formed of three contiguous sections each in fluid communication with each other, a first section adjacent the receiving end and extending substantially vertically from the vent, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at an angle relative to the second section in plan view so that the third section is oriented substantially horizontally.
 236. The apparatus of claim 235, wherein at least a part of the vent upstream of the first section is substantially horizontally disposed so that the fluids flowing therethrough are flowing substantially horizontally.
 237. The apparatus of claim 235, wherein the first section is oriented at from about a 0 to about a 60 degree angle relative to the vertical plane, the second section is oriented at from about aa 5 to about an 85 degree angle relative to the vertical plane, and the third section is oriented at from about a 0 to about a 45 degree angle relative to the horizontal plane.
 238. The apparatus of claim 235, wherein the first section is oriented at about a 0 degree angle relative to the vertical plane, the second section is oriented at about a 45 degree angle relative to the vertical plane, and the third section is oriented at about a 0 degree angle relative to the horizontal plane.
 239. The process of claim 184, wherein the polycondensation pipe reactor has a length of at least 20 feet.
 240. The process of claim 184, wherein the polycondensation pipe reactor has a length of at least 60 feet.
 241. The process of claim 239 or 240, wherein the first end is disposed vertically above the second end, and the polycondensation fluids flow down the pipe reactor by gravity.
 242. The process of claim 241, wherein the pipe reactor comprises substantially empty pipe.
 243. The apparatus of claim 214, wherein the pipe reactor has a length of at least 20 feet.
 244. The apparatus of claim 214, wherein the pipe reactor has a length of at least 60 feet.
 245. A process for making an ester from a plurality of reactants comprising: (a) providing an esterification pipe reactor having a first inlet and a first outlet; (b) adding the reactants under esterification reaction conditions into the esterification pipe reactor proximate to the first inlet and forming a two phase flow so the reactants form a liquid phase and vapor phase through the esterification pipe reactor and wherein at least a portion of the reactants form an ester monomer.
 246. The process of claim 245 wherein at least a portion of the ester monomer is reacted in the esterification pipe reactor to form an ester oligomer.
 247. The process of claim 246 further comprising: (c) reacting the ester oligomer under polycondensation reaction conditions in a polycondensation pipe reactor wherein at least a portion of the oligomer forms a polyester.
 248. The process of claim 245 further comprising: (c) reacting the ester monomer under polycondensation reaction conditions in a polycondensation pipe reactor wherein at least a portion of the ester monomer forms an ester oligomer.
 249. The process of claim 248 further comprising: (d) reacting the ester oligomer under polycondensation reaction conditions in the polycondensation pipe reactor wherein at least a portion of the oligomer forms a polyester.
 250. The process of claim 245 wherein said reactants include a diacid or diacid generator and a diol or diol generator.
 251. The process of claim 250 wherein said diacid or diacid generator is selected from the group consisting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms and esters of these diacids; and wherein said diol or diol generator is selected from the group consisting cycloaliphatic diols having 6 to 20 carbon atoms and aliphatic diols having 3 to 20 carbon atoms.
 252. The process of claim 250 wherein said diacid or diacid generator and a diol or diol generator are selected from the group consisting of terephthalic acid, phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid, dipheny-3,4′-dicarboxylic acid, 2,2,-dimethyl-1,3-propandiol, dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dimethyl terephthalate, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-cyclohexane-dimethanol, propane-1,3-diol, pentane-1,5-diol, hexane-1,6-diol, neopentylglycol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol-(1,3), 2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-(1,3), hexanediol-(1,3), 1,4-di-(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy- 1,1,3,3-tetramethyl-cyclobutane, 2,2,4,4 tetramethylcyclobutanediol, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, 2,2-bis-(4-hydroxypropoxyphenyl)-propane, isosorbide, hydroquinone, BDS-(2,2-(sulfonylbis)4,1-phenyleneoxy))bis(ethanol), and mixtures thereof.
 253. The process of any one of claims 245 to 252 wherein said ester is poly(ethylene terephthalate)
 254. The process of claim 250, 251 or 252 wherein said diacid or diacid generator are selected from the group consisting of terephthalic acid and dimethyl terephthalate, and said diol is ethylene glycol.
 255. The process of any one of claims 245 to 249 wherein at least one of the pipe reactors has a means for recycling a portion of the process fluid, and the process includes recycling a portion of the process fluid to the esterification pipe reactor.
 256. The process of any one of claims 247 to 249 wherein at least one of the pipe reactors has a means for recycling a portion of the process fluid, and the process includes feeding a portion of the process fluid to the polycondensation pipe reactor.
 257. The process of claim 255 further comprising adding at least one reactant into the recycled process fluid.
 258. The process of any one of claims 247, 248, or 249 wherein the polycondensation pipe reactor has a plurality of zones or stages and the process includes operating at least two of the zones or stages at a pressure differential.
 259. The process of any one of claims 245 to 249 further comprising removing a portion of the vapor from at least one of the pipe reactors.
 260. The process of claim 259 comprising operating the esterification pipe reactor in a bubble or froth regime.
 261. The process of claim 258 comprising operating the polycondensation pipe reactor in a stratified flow regime.
 262. The process of claim 245 further including adding to the pipe reactor at least one material selected from a catalytic material, colorant, toner, pigment, carbon black, glass fiber, filler, impact modifier, antioxidant, stabilizer, flame retardant, reheat aid, acetaldehyde reducing compound, oxygen scavenging compound, UV absorbing compound, barrier improving additive, black iron oxide and mixtures thereof.
 263. The process of claims 245 to 249, 260, or 261 wherein the pipe reactor is a substantially empty pipe.
 264. The process of any one of claims 245 to 249 includes operating the esterification pipe reactor with a pressure profile between the first inlet and the first outlet and wherein the pressure at the first inlet is greater than the pressure at the first outlet.
 265. The process of claim 264 includes establishing the pressure profile by a hydrostatic pressure inside the esterification pipe reactor.
 266. The process of claims 247 to 249 further comprising controlling the pressure between the esterification process and polycondensation process using a seal leg in fluid communication with and positioned between the esterification pipe reactor and the polycondensation pipe reactor.
 267. The process of claim 266 further comprising heating the fluid in said seal leg.
 268. The process of claim 267 wherein the fluid in the seal leg is heated to a boiling temperature.
 269. The process of claim 259 further comprising recovering reactants from the removed vapor to form a reactant lean overhead product and a reactant rich bottom product.
 270. The process of claim 259 further comprising oxidizing the removed vapor an oxidizer selected from a heat transfer media furnace, an incinerator or a thermal oxidizer.
 271. The process of claim 269 further comprising oxidizing the reactant lean overhead product in an oxidizer selected from a heat transfer media furnace, an incinerator or a thermal oxidizer.
 272. The process of claim 269 includes recycling the reactant rich bottom product to the esterification pipe reactor.
 273. The process of any one of claims 269-272 wherein at least one of said reactants is glycol.
 274. The process of any one of claims 245 to 249 further comprising retrofitting said pipe reactor to a conventional polyester process having at least one continuous stirred tank reactor.
 275. A process for making a polyester from a plurality of reactants comprising: (a) providing an esterification pipe reactor having a first inlet and a first outlet; (b) adding the reactants under esterification reaction conditions into the esterification pipe reactor proximate to the first inlet and forming a two phase flow so the reactants form a liquid phase and vapor phase flow through the esterification pipe reactor and wherein at least a portion of the reactants form an ester monomer; (c) reacting the monomer under polycondensation reaction conditions in a polycondensation pipe reactor wherein at least a portion of the ester monomer forms an oligomer; and (d) reacting the oligomer under polycondensation reaction conditions in the polycondensation pipe reactor wherein at least a portion of the oligomer forms a polyester.
 276. An apparatus for preparing of at least one of an ester monomer, an ester oligomer or a polyester comprising a pipe reactor having an inlet, an outlet and an interior through which reactants of at least one of an ester monomer, an ester oligomer or a polyester are passed.
 277. The apparatus of claim 276 wherein the pipe reactor is an esterification pipe reactor having a first inlet, a first outlet, a first inner surface and a first interior for passing reactants through.
 278. The apparatus of claim 276 the pipe reactor is a polycondensation pipe reactor having a second inlet, a second outlet, a second inner surface and a second interior for passing reactants through.
 279. The apparatus of claim 276 wherein the pipe reactor comprises: (a) an esterification pipe reactor having a first inlet, a first outlet, a first inner surface and a first interior for passing reactants through; and (b) a polycondensation pipe reactor having a second inlet, a second outlet, a second inner surface and a second interior for passing reactants through.
 280. The apparatus of any one of claims 277 to 279 further includes a fluid restricting means affixed to at least one of the inner surfaces.
 281. The apparatus of claim 280 wherein the fluid restricting means includes a weir for partially blocking the flow of the fluids.
 282. The apparatus of claim 279 wherein the second inlet and the first outlet are in fluid communication.
 283. The apparatus of claim 277 or 279 wherein the first outlet is elevationally above the first inlet.
 284. The apparatus of any one of claims 277 to 279 further includes a means for recirculating at least a portion of fluid materials in at least one of the pipe reactors.
 285. The apparatus of claim 277 or 279 further includes a means for recirculating at least a portion of fluid materials, wherein the recirculating means includes an influent and an effluent, and wherein the effluent is in fluid communication with the esterification pipe reactor.
 286. The apparatus of claim 285 wherein the recirculating means effluent is located proximate to the first inlet of the esterification pipe reactor.
 287. The apparatus of claims 276 to 279 or 281 further comprising a means for venting, degassing or removing vapors from at least a portion of the interior.
 288. The apparatus of claim 287 wherein the venting or degassing means includes at least one of: (a) a linear stand pipe; (b) a linear stand pipe having a liquid entrainment separator in-line with the vapor path; and (c) a non-linear stand pipe disposed vertically above the pipe reactor and formed of three contiguous sections each in fluid communication with the adjacent section, a substantially vertical first section in fluid communication with the pipe reactor, a second section coupled to the first section and oriented at an angle relative to the first section in plan view, and a third section coupled to the second section and oriented at a complimentary angle relative to the second section that the third section is oriented substantially horizontally such that the non-linearity causes all or most of the liquid droplets in the vapor to impinge on some surface of the vent piping; or (d) a pressure decreasing device selected from an eductor, a siphon, an exhauster, a venturi nozzle, or a jet.
 289. The apparatus of claim 278, 279 or 281 wherein the polycondensation reactor has a plurality of zones, stages or sections wherein a zone is defined by a relative pressure differential and wherein a seal leg is positioned between and in fluid communication with each zone, stage or section for controlling the pressure between reactor sections.
 290. The apparatus of claim 281 wherein at least one pipe reactor includes a flow inverter.
 291. The apparatus of 290 wherein the flow inverter is proximate to and downstream of the weir.
 292. The apparatus of claim 276 wherein the pipe reactor relative to a length has alternating linear and non-linear sections between the inlet and outlet thereof.
 293. The apparatus of any one of claims 276 to 278 having a means for heating the reactants in the pipe reactor.
 294. The apparatus of claim 293 wherein the heating means includes at least one of: (a) a jacket around an exterior surface of the pipe reactor which defines an annular space through which a heat transfer medium is circulated; (b) a plurality of electrical heating components wrapped about the exterior surface of the pipe reactor; or (c) a heat exchanger along at least a portion of the pipe reactor whereby the reactants are passed to bring the temperature back up as the by-product vaporizes.
 295. The apparatus of claim 294 wherein the heat transfer medium is selected from oil, water, vapor, or mixtures thereof.
 296. The apparatus of any one of claims 276 to 278 wherein the pipe reactor is divided into a plurality of substantially parallel flow conduits extending between the inlet and the outlet thereof, and wherein the reactants flowing through the pipe reactor pass through at least one of the plurality of flow conduits while flowing through the reactor.
 297. The apparatus of claim 294 wherein the heating means further comprises a heat transfer media control system having a supply heat transfer media loop through which a first stream of a heat transfer media is passed and a return heat transfer media loop through which a second stream of the heat transfer media is passed, the temperature of the first heat transfer media stream being greater than the temperature of the second heat transfer media stream, the heat transfer media control system including: (a) a first heat transfer media header through which the first heat transfer media stream is passed; (b) a second heat transfer media header through which the second heat transfer media stream is passed; (c) a first heat transfer media sub-loop, through which the heat transfer media may be passed, from the first to the second headers, respectively; (d) a control valve in fluid communication with a selected one of the headers and the first sub-loop; wherein the pressure of the first heat transfer media stream within the first header being greater than the pressure of the second heat transfer media stream within the second header and the control valve is used to selectively direct at least a portion of the first heat transfer media stream into the first sub-loop using the pressure of the first heat transfer media stream to pass the heat transfer media, and to also control the temperature and pressure of the heat transfer media stream being passed through the first sub-loop.
 298. The apparatus of claim 297 further comprising: (a) a second heat transfer media sub-loop formed separately of the first sub-loop and in fluid communication therewith; and (b) a second control valve in fluid communication with the second sub-loop; wherein the second control valve selectively directs at least a portion of the first heat transfer media stream into the second sub-loop to control the temperature and the pressure of the heat transfer media being passed through the second sub-loop.
 299. The apparatus of claim 276-279, 288, 292, 294 or 295 wherein said pipe reactor is a substantially empty pipe.
 300. The apparatus of claim 282 further comprising a seal leg in fluid communication with and positioned between the esterification pipe reactor and the polycondensation pipe reactor for controlling the pressure between the esterification process and polycondensation process.
 301. The apparatus of claim 300 wherein the seal leg includes a means for heating fluid in the seal leg.
 302. The apparatus of claim 301 wherein said heating means is a heat exchanger positioned adjacent to the seal leg.
 303. The apparatus of claim 301 wherein said heating means is a heat exchanger positioned in line with the seal leg.
 304. The apparatus of claim 287 further comprising a means for recovering reactants from the removed vapor to form a reactant lean overhead product and a reactant rich bottom product.
 305. The apparatus of claim 304 wherein said recovery means includes at least one of a water column, a stripper column or a mixed glycol and monomer column.
 306. The apparatus of claim 304 further comprising a means for oxidizing reactant lean overhead product wherein the oxidizer is selected from a heat transfer media furnace, an incinerator or a thermal oxidizer.
 307. The apparatus of claim 287 further comprising means for oxidizing reactant lean overhead product wherein the oxidizer is selected from a heat transfer media furnace, an incinerator or a thermal oxidizer.
 308. The apparatus of claim 276-279, 282, 288, 290, 297, 300 or 304 wherein said pipe reactor is retrofitted to a conventional polyester process having at least one continuous stirred tank reactor. 